docs(kyberforge): add ADR-0016, agent tools-field omitted at plugin scope

#89's grilling session surfaced a real upstream gap: APM's agent
primitive has no per-target compile integrator, so tools: and every
Claude-only field (isolation, maxTurns, effort, memory, permissionMode)
would verbatim-copy into Copilot's file with an incompatible or
unrecognized shape. Omitting them entirely is the only option that
never ships a wrong value to a real harness.

Scoped to plugin-scope agent-author only — project/user scope keep
today's Claude+Copilot pair model unchanged. Partially supersedes
ADR-0005 and ADR-0008's plugin-scope clauses (addenda appended to
both); ADR-0009's field-inventory.md mechanism is unaffected, only
its plugin-scope content shape changes.

Refs: #89

docs/adr/0005-agent-author-dual-provider-scaffold.md

@@ -44,3 +44,8 @@ separate single-provider skill, adding complexity with no benefit.
 file now lives at `<plugin-root>/sources.md`, outside the `agents/` directory, because
 `claude plugin validate --strict` auto-discovers every `.md` under `agents/` as an agent
 requiring frontmatter. See ADR-0010 for the empirical finding and rationale.
+
+**Update (ADR-0016):** the plugin-scope clause above is superseded. Plugin scope is no longer
+detected via `plugin.json`, and no longer produces a Claude+Copilot file pair — a directory
+containing `apm.yml` now gets a single vendor-neutral `.apm/agents/<name>.agent.md` file with
+no provider-specific fields. Project scope and user scope are unaffected. See ADR-0016.

docs/adr/0008-agent-audit-single-file-invocation.md

@@ -14,3 +14,9 @@
 - Scope detection walks up from the input file: first directory containing `plugin.json` → plugin scope; first directory containing `.git` without `plugin.json` → project scope; path under `~` with neither → user scope.
 - At user scope the derivation crosses filesystem locations (`~/.claude/agents/` ↔ `~/.copilot/agents/`); the script must handle the home directory case explicitly.
 - The invocation signature is the public contract. Changing it is a breaking change to any caller — treat it as such.
+
+**Update (ADR-0016):** the plugin-scope clause above is superseded. Plugin scope is no longer
+detected via `plugin.json`, and there is no counterpart to derive — a directory containing
+`apm.yml` produces a single `.apm/agents/<name>.agent.md` file, and `agent-audit` validates it
+directly with no pair-consistency check. Project scope and user scope keep the pair-derivation
+mechanism described above unchanged. See ADR-0016.

docs/adr/0016-apm-agent-primitive-drops-provider-specific-fields.md

@@ -0,0 +1,88 @@
+# Plugin-scope agent-author omits `tools:` and all Claude-only fields from `.apm/agents/*.agent.md`
+
+This ADR is a narrower, downstream consequence discovered while designing issue #89's
+implementation under ADR-0015's broader direction (Microsoft APM replaces hand-authored
+plugin/marketplace authoring). It does not restate ADR-0015's rationale — see that ADR for
+the parent decision.
+
+## Context
+
+APM's agent primitive (`.apm/agents/<name>.agent.md`) has no per-target integrator in
+`apm compile` — confirmed via APM's own Python source (`integration/targets.py` and related
+files, cited in `plugins/kyberforge/docs/research/docs/microsoft-apm/agent-primitive-schema.md`).
+Compilation does a naive verbatim copy of the whole frontmatter and body to both the Claude
+Code and Copilot CLI targets. This is unlike:
+
+- The **skill** primitive, which is also a straight copy (confirmed in the same research doc)
+  but has no field semantics to conflict — `SKILL.md`'s content is target-agnostic already.
+- The **prompt**, **instructions**, and **hooks** primitives, which each get real per-target
+  reconstruction through a dedicated integrator (field allowlisting, key renaming, dropped-field
+  warnings).
+
+Because the agent primitive ships the same frontmatter unchanged to both harnesses, two
+concrete incompatibilities surface:
+
+1. **`tools:`** — Claude Code expects a space-separated tool-name string; Copilot CLI expects a
+   list drawn from its own alias vocabulary (`execute`/`read`/`edit`/`search`/`agent`/`web`). A
+   value correct for one harness is wrong for the other.
+2. **Claude-only knobs with no Copilot equivalent** — `isolation`, `maxTurns`, `effort`,
+   `memory`, `permissionMode`. Writing any of these means Copilot's copy carries frontmatter
+   keys it doesn't recognize at all. Whether Copilot's agent loader ignores unknown keys or
+   errors on them is unconfirmed by research.
+
+## Decision
+
+At **plugin scope only** (destination package has an `apm.yml` at its root — an APM producer
+package compiled via `apm compile`), `.apm/agents/<name>.agent.md` carries only `name`,
+`description`, `model`, and the prose body. No `tools:` field, no Claude-only fields, at all.
+
+Absent `tools:` means inherit-all-tools on both harnesses — the one value that is never wrong
+on either target, unlike a present, harness-specific value that is guaranteed wrong on at least
+one of them.
+
+`agent-audit`, at plugin scope, flags — as a **SUGGESTION**, not a FAIL, since this is an
+upstream schema limitation rather than an authoring mistake — any agent whose description or
+body implies a need for tool restriction or a Claude-only behavior the frontmatter can no
+longer express. This gives visibility into the gap without pretending the schema can do
+something it can't.
+
+### Scope boundary
+
+This decision applies to **plugin-scope `agent-author` only**. Project scope (`.claude/agents/`
++ `.github/agents/`) and user scope (`~/.claude/agents/` + `~/.copilot/agents/`) are not APM
+packages — neither goes through `apm compile` — so both keep today's dual-file Claude+Copilot
+pair model exactly as ADR-0005 and ADR-0008 already describe. Those two ADRs remain fully
+authoritative for project and user scope; only their plugin-scope clauses are affected by this
+ADR (see the update notes appended to each).
+
+## Considered options
+
+**Pick one harness's vocabulary and accept breakage on the other (rejected).** E.g. always
+write Claude's space-separated `tools:` string. Rejected because it ships a value that is
+silently wrong (or possibly a hard error) on Copilot, and which harness "wins" would be an
+arbitrary, undocumented asymmetry.
+
+**Same as above, but `agent-audit` flags the cross-harness breakage as a tracked finding
+(rejected).** Rejected for the same core reason — it still ships a wrong value to a real
+harness. Tracking the breakage doesn't prevent it, and the chosen decision already gets
+equivalent visibility (a SUGGESTION finding) without ever shipping the wrong value in the first
+place.
+
+## Consequences
+
+- Every plugin-scope APM agent loses per-agent tool restriction and any Claude-only capability
+  (isolation, maxTurns, effort, memory, permissionMode) until APM ships a real per-target
+  integrator for the agent primitive. This is a known, accepted regression, not an oversight.
+- **ADR-0005 is partially superseded** — its plugin-scope clause ("directory containing
+  `plugin.json` is plugin scope → both files land in `<root>/agents/`") no longer applies.
+  Plugin scope is now "directory containing `apm.yml` → single vendor-neutral file lands in
+  `<root>/.apm/agents/`." Project and user scope, and the rest of ADR-0005, are unaffected.
+- **ADR-0008 is partially superseded** — its counterpart-derivation/pair-validation mechanism
+  no longer applies at plugin scope; `agent-audit` takes the single file directly there. Project
+  and user scope, where a real pair still exists, are unaffected.
+- **ADR-0009 is not superseded.** The mechanism it established — `agent-audit` reading field
+  lists from `references/field-inventory.md` rather than hardcoding them, with a `source_keys`
+  provenance chain — survives and is reused. Only the *content shape* changes for plugin scope:
+  `field-inventory.md` shifts from two side-by-side CC-only/Copilot-only blocklists to one
+  vendor-neutral allowlist (`name`/`description`/`model`) for plugin-scope agents, while
+  continuing to serve its original two-blocklist role for project/user-scope validation.