docs: trim skill READMEs and ADR/changelog narration

Two related simplification-audit findings, bundled because they edit
some of the same skill-audit files and splitting would fragment
single-file diffs.

Finding 10: delete 48 per-skill/reference README.md files (they
restated SKILL.md in narrative form and no agent ever loads them) plus
2 scaffold templates. Drop the README criterion from skill-audit's
file-structure.md and finding-criteria.md, and the README-generation
step from skill-author's new-skill.sh; update new-skill.bats to match.
Plugin-root READMEs are kept intentionally, out of scope.

Finding 12: strip historical ADR-0020/ADR-0023 citations and
changelog-style narration from model-facing skill content across
kyberforge and git plugin skills. Delete skill-author's one-time
retrofit.md migration guide and its references. Some ADR-0023 tags
were not narration but check-rtk-prefix's required opt-out marker for
intentionally-bare git commands -- those were restored, not stripped.

Mirror re-synced and full pre-commit/pre-push suite verified green.

Refs: SIMPLIFICATION-AUDIT.md findings 10, 12

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YR2CjVumUbEGWcMikcoXBD

plugins/git/skills/git-branches/SKILL.md

@@ -9,7 +9,7 @@ description: >
   Not a Gitea remote's branches -> `gitea-branches`.
 
 metadata:
-  version: "1.0.1"
+  version: "1.0.2"
   category: git
   source_keys:
     - context7-git-htmldocs
@@ -21,7 +21,7 @@ metadata:
 ## Gotchas
 
 - **Uncommitted changes abort a switch.** `git switch` refuses rather than clobbering conflicting local edits. Offer to stash and retry — forcing the checkout past it is how work disappears.
-- **A branch and a tag can carry the same name.** Detect it before acting — `git branch --list <name>` (bare, not `rtk`: rtk prints a phantom `* ` line even on no match, which reports every name as ambiguous — ADR-0023) and `rtk git tag --list <name>`; output from both means the name is ambiguous. Prefer `git switch` over `git checkout`, and where a command accepts either ref, disambiguate with `refs/heads/<name>` or `refs/tags/<name>`.
+- **A branch and a tag can carry the same name.** Detect it before acting — `git branch --list <name>` (bare, not `rtk`: rtk prints a phantom `* ` line even on no match, which reports every name as ambiguous) and `rtk git tag --list <name>`; output from both means the name is ambiguous. Prefer `git switch` over `git checkout`, and where a command accepts either ref, disambiguate with `refs/heads/<name>` or `refs/tags/<name>`.
 - **`main` and `master` are a refusal, not a gate.** Force-pushing, force-deleting, or renaming them is rejected even when the caller passes `confirm: true` — no flag makes the remote's history recoverable. Offer a new branch instead.
 
 ## Step 1 — Determine the branching pattern