refactor(core): retrofit agentsmd-author to the ADR-0020 context contract

Description 960 -> 244 chars, body 470 -> 452 words, Gotchas 36% -> 22%.
Both composition notes move to README.md, which already carried them.

Four of five Gotchas were paraphrases of the step below them and were
deleted with their force folded back into that step. A clean-context
audit overturned the fifth deletion: the provider-file prohibition was
strictly broader than Step 4, so it was never a paraphrase, and Step 4's
'don't rewrite it yourself' is attached to the if-duplicates branch. With
Write and Edit granted, a provider file that was merely stale had nothing
forbidding an edit. Restored as an unconditional Gotcha, read before any
step writes.

Also restores a concrete indirect trigger. The retrofit had replaced two
with the meta-statement 'even when they don't name the file', which
claims an indirect trigger exists rather than being one -- and users
asking to document a repo for AI tools have no reason to know the
filename.

Refs #99

plugins/core/.apm/skills/agentsmd-author/SKILL.md

@@ -1,20 +1,10 @@
 ---
 name: agentsmd-author
 description: >
-  Use when the user wants to create or update a repo's AGENTS.md file
+  Use when the user wants a repo's AGENTS.md written or updated, root or
-  ("write an AGENTS.md for this repo", "add setup/test instructions for
+  nested, including "document this for AI coding tools". Writes only verified
-  agents", "update AGENTS.md", "give this package its own AGENTS.md") — even
+  conventions. Not review-only -> `agentsmd-audit`. Not for CLAUDE.md ->
-  if they don't name the file explicitly, e.g. "document this for AI coding
+  `provider-adapter-author`.
-  tools" or "make sure agents know how to run tests here". Writes/updates
-  AGENTS.md by exploring the target repo for real build, test, lint, and
-  style conventions — never invents commands. Supports nested monorepo
-  placement (a subdirectory can get its own AGENTS.md following
-  nearest-file-wins precedence). Closes every run by invoking agentsmd-audit
-  inline, and calls provider-adapter-author when an existing provider file
-  (CLAUDE.md, etc.) now duplicates what AGENTS.md owns. Do not use to review
-  an existing AGENTS.md without changing it — use agentsmd-audit instead. Do
-  not use to convert CLAUDE.md/.cursor/rules into a thin adapter — use
-  provider-adapter-author instead.
 allowed-tools: Bash Read Write Edit
 metadata:
   category: docs
@@ -22,16 +12,13 @@ metadata:
     - agents-md-official
     - context7-websites-agents-md
     - context7-agentsmd-agents-md
-  version: "0.1.1"
+  version: "0.1.2"
 ---
 
 ## Gotchas
 
 - Never invent a command. Every line under a setup/test/build section must come from something you actually found in the repo (`package.json` scripts, a `Makefile` target, a CI workflow step, a README). If you can't verify a command, don't include it.
-- AGENTS.md has no required schema — don't force every common-sections-checklist heading into every repo. Include only sections that reflect something real about this repo; a thin, accurate file beats a padded, generic one.
+- Never write to a provider file yourself, in any circumstance: `CLAUDE.md`, `.cursor/rules/*.mdc`, `.github/copilot-instructions.md` and their equivalents are `provider-adapter-author`'s to own. That holds even when the user asks for one in the same breath as AGENTS.md, and even when the file is merely stale or missing a pointer rather than duplicating anything. Detect it and hand off.
-- Nested placement is for genuinely different conventions, not convenience. Only create a subdirectory AGENTS.md when that subtree has its own build tool, stack, or conventions distinct from the root — otherwise you're duplicating content the root already covers, which the nearest-file-wins rule doesn't merge back together.
-- This skill never touches CLAUDE.md, `.cursor/rules/*.mdc`, `copilot-instructions.md`, or similar provider files directly — that's `provider-adapter-author`'s job. Detect and hand off; don't reconcile it yourself.
-- This skill never audits on its own judgment — the closing `agentsmd-audit` invocation is mandatory, not optional, even when the change looks trivial.
 
 ## Step 1 — Explore the target repo
 
@@ -40,17 +27,17 @@ Before writing anything, gather real facts: package manager and scripts (`packag
 ## Step 2 — Decide placement
 
 - No `AGENTS.md` at the repo root yet → create one there first, covering whole-repo conventions.
-- A subdirectory has materially different build/test tooling or conventions than the root → create or update a nested `AGENTS.md` there, scoped to what's different. Don't repeat root-level content — the nearest-file-wins rule means the nested file is read alone, not merged with the root.
+- A subdirectory has materially different build/test tooling or conventions than the root → create or update a nested `AGENTS.md` there, scoped to what's different. Convenience is not a reason to create one — without a distinct stack you are duplicating content the root already covers. **Don't repeat root-level content** in a nested file: the nearest-file-wins rule means it is read alone, never merged back with the root.
 - Otherwise → update the existing file(s) in place.
 
 ## Step 3 — Write or update
 
-Use only sections that reflect something real about the repo — never fill in every common-sections-checklist heading just because it exists. Read `references/content-guide.md` for section-by-section guidance, a worked example, and what separates useful content from generic padding, before writing.
+AGENTS.md has no required schema. Use only sections that reflect something real about the repo — never fill in every common-sections-checklist heading just because it exists, because a thin accurate file beats a padded generic one. Read `references/content-guide.md` for section-by-section guidance, a worked example, and what separates useful content from generic padding, before writing.
 
 ## Step 4 — Check for an existing provider file
 
-Look for `CLAUDE.md`, `.cursor/rules/*.mdc`, `.github/copilot-instructions.md`, or similar in the target repo. If one exists and now duplicates content the AGENTS.md you just wrote/updated already owns, invoke the `provider-adapter-author` skill on it to reconcile — don't rewrite it yourself.
+Look for `CLAUDE.md`, `.cursor/rules/*.mdc`, `.github/copilot-instructions.md`, or similar in the target repo. If one exists and now duplicates content the AGENTS.md you just wrote/updated already owns, invoke the `provider-adapter-author` skill on it to reconcile.
 
 ## Step 5 — Audit and report
 
-Invoke the `agentsmd-audit` skill directly on the AGENTS.md file(s) you just wrote or updated. Resolve any FAIL findings before considering the work done — re-invoke this skill's own writing steps to fix them, then re-run the audit, same as any other close-the-loop check. Report what was created/changed, whether a provider file was reconciled, and the audit's final result.
+Invoke the `agentsmd-audit` skill directly on the AGENTS.md file(s) you just wrote or updated. This closeout is mandatory, not optional, even when the change looks trivial — never sign the work off on your own judgment. Resolve any FAIL findings before considering the work done — re-invoke this skill's own writing steps to fix them, then re-run the audit, same as any other close-the-loop check. Report what was created/changed, whether a provider file was reconciled, and the audit's final result.

plugins/core/skills/agentsmd-author/SKILL.md

@@ -1,20 +1,10 @@
 ---
 name: agentsmd-author
 description: >
-  Use when the user wants to create or update a repo's AGENTS.md file
+  Use when the user wants a repo's AGENTS.md written or updated, root or
-  ("write an AGENTS.md for this repo", "add setup/test instructions for
+  nested, including "document this for AI coding tools". Writes only verified
-  agents", "update AGENTS.md", "give this package its own AGENTS.md") — even
+  conventions. Not review-only -> `agentsmd-audit`. Not for CLAUDE.md ->
-  if they don't name the file explicitly, e.g. "document this for AI coding
+  `provider-adapter-author`.
-  tools" or "make sure agents know how to run tests here". Writes/updates
-  AGENTS.md by exploring the target repo for real build, test, lint, and
-  style conventions — never invents commands. Supports nested monorepo
-  placement (a subdirectory can get its own AGENTS.md following
-  nearest-file-wins precedence). Closes every run by invoking agentsmd-audit
-  inline, and calls provider-adapter-author when an existing provider file
-  (CLAUDE.md, etc.) now duplicates what AGENTS.md owns. Do not use to review
-  an existing AGENTS.md without changing it — use agentsmd-audit instead. Do
-  not use to convert CLAUDE.md/.cursor/rules into a thin adapter — use
-  provider-adapter-author instead.
 allowed-tools: Bash Read Write Edit
 metadata:
   category: docs
@@ -22,16 +12,13 @@ metadata:
     - agents-md-official
     - context7-websites-agents-md
     - context7-agentsmd-agents-md
-  version: "0.1.1"
+  version: "0.1.2"
 ---
 
 ## Gotchas
 
 - Never invent a command. Every line under a setup/test/build section must come from something you actually found in the repo (`package.json` scripts, a `Makefile` target, a CI workflow step, a README). If you can't verify a command, don't include it.
-- AGENTS.md has no required schema — don't force every common-sections-checklist heading into every repo. Include only sections that reflect something real about this repo; a thin, accurate file beats a padded, generic one.
+- Never write to a provider file yourself, in any circumstance: `CLAUDE.md`, `.cursor/rules/*.mdc`, `.github/copilot-instructions.md` and their equivalents are `provider-adapter-author`'s to own. That holds even when the user asks for one in the same breath as AGENTS.md, and even when the file is merely stale or missing a pointer rather than duplicating anything. Detect it and hand off.
-- Nested placement is for genuinely different conventions, not convenience. Only create a subdirectory AGENTS.md when that subtree has its own build tool, stack, or conventions distinct from the root — otherwise you're duplicating content the root already covers, which the nearest-file-wins rule doesn't merge back together.
-- This skill never touches CLAUDE.md, `.cursor/rules/*.mdc`, `copilot-instructions.md`, or similar provider files directly — that's `provider-adapter-author`'s job. Detect and hand off; don't reconcile it yourself.
-- This skill never audits on its own judgment — the closing `agentsmd-audit` invocation is mandatory, not optional, even when the change looks trivial.
 
 ## Step 1 — Explore the target repo
 
@@ -40,17 +27,17 @@ Before writing anything, gather real facts: package manager and scripts (`packag
 ## Step 2 — Decide placement
 
 - No `AGENTS.md` at the repo root yet → create one there first, covering whole-repo conventions.
-- A subdirectory has materially different build/test tooling or conventions than the root → create or update a nested `AGENTS.md` there, scoped to what's different. Don't repeat root-level content — the nearest-file-wins rule means the nested file is read alone, not merged with the root.
+- A subdirectory has materially different build/test tooling or conventions than the root → create or update a nested `AGENTS.md` there, scoped to what's different. Convenience is not a reason to create one — without a distinct stack you are duplicating content the root already covers. **Don't repeat root-level content** in a nested file: the nearest-file-wins rule means it is read alone, never merged back with the root.
 - Otherwise → update the existing file(s) in place.
 
 ## Step 3 — Write or update
 
-Use only sections that reflect something real about the repo — never fill in every common-sections-checklist heading just because it exists. Read `references/content-guide.md` for section-by-section guidance, a worked example, and what separates useful content from generic padding, before writing.
+AGENTS.md has no required schema. Use only sections that reflect something real about the repo — never fill in every common-sections-checklist heading just because it exists, because a thin accurate file beats a padded generic one. Read `references/content-guide.md` for section-by-section guidance, a worked example, and what separates useful content from generic padding, before writing.
 
 ## Step 4 — Check for an existing provider file
 
-Look for `CLAUDE.md`, `.cursor/rules/*.mdc`, `.github/copilot-instructions.md`, or similar in the target repo. If one exists and now duplicates content the AGENTS.md you just wrote/updated already owns, invoke the `provider-adapter-author` skill on it to reconcile — don't rewrite it yourself.
+Look for `CLAUDE.md`, `.cursor/rules/*.mdc`, `.github/copilot-instructions.md`, or similar in the target repo. If one exists and now duplicates content the AGENTS.md you just wrote/updated already owns, invoke the `provider-adapter-author` skill on it to reconcile.
 
 ## Step 5 — Audit and report
 
-Invoke the `agentsmd-audit` skill directly on the AGENTS.md file(s) you just wrote or updated. Resolve any FAIL findings before considering the work done — re-invoke this skill's own writing steps to fix them, then re-run the audit, same as any other close-the-loop check. Report what was created/changed, whether a provider file was reconciled, and the audit's final result.
+Invoke the `agentsmd-audit` skill directly on the AGENTS.md file(s) you just wrote or updated. This closeout is mandatory, not optional, even when the change looks trivial — never sign the work off on your own judgment. Resolve any FAIL findings before considering the work done — re-invoke this skill's own writing steps to fix them, then re-run the audit, same as any other close-the-loop check. Report what was created/changed, whether a provider file was reconciled, and the audit's final result.