docs: dedupe .apm/-mirror and apm.lock/SessionStart restatements (finding 29)

README and AGENTS.md each fully restated the "edit .apm/, never the
mirror" rule and the apm.lock/SessionStart mechanism instead of linking
to their canonical sources (architecture.md, ADR-0019).

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

AGENTS.md

@@ -11,11 +11,7 @@ This file carries only what applies to **every** session. Setup, prerequisites,
 
 ## Edit `.apm/`, never the flat mirror
 
-`plugins/<name>/.apm/` is the only hand-edited source for plugin content. The flat `plugins/<name>/{skills,agents,commands,instructions,extensions}/` directories, the merged `plugins/<name>/hooks/hooks.json`, and both `plugin.json` manifests are generated — nothing marks them as generated, so check the path before you edit. An edit to the mirror is discarded by the next sync and reported as drift by the `check-plugin-content-sync` pre-push hook.
-
-Not everything in a plugin root is generated. `README.md`, `docs/`, `bin/`, `sources.md`, `.mcp.json` and per-plugin extras are hand-authored there with no `.apm/` source — edit those in place. The rule is per-path, not per-directory. But a file placed *inside* a mirrored directory is deleted on the next sync (`sync_dir` runs `rm -rf` before every copy), so plugin-root documentation goes in `docs/`, never in `hooks/` or `skills/`.
-
-Full model: `docs/spec/architecture.md`.
+`plugins/<name>/.apm/` is the only hand-edited source for plugin content — the generated flat mirror and manifests are discarded on the next sync and reported as drift by `check-plugin-content-sync`. What's exempt (`README.md`, `docs/`, `bin/`, `sources.md`, `.mcp.json`) and why: `docs/spec/architecture.md`.
 
 ## Prefer plugin skills over raw shell
 
@@ -34,7 +30,7 @@ Fall back to raw shell only when no skill covers it.
 ## Session rules
 
 - **Do not add repo-owned keys to `.claude/settings.json`.** apm treats it as its own deployed artifact and `apm audit --ci` replays the install and diffs, so anything apm would not have written is permanent drift that fails the `apm-audit-ci` pre-push hook. A hook you want here is authored in `plugins/<name>/.apm/hooks/` and deployed by apm, never hand-written into that file. The `SessionStart` entry already in it is exactly that: kyberforge authors it in `plugins/kyberforge/.apm/hooks/hooks.json` and apm merges it in, so it is apm's own output, it is what the replay expects, and it belongs in the commit — do not strip it (ADR-0019). Machine-specific settings go in the gitignored `.claude/settings.local.json`; shared enforcement goes in `.pre-commit-config.yaml`.
-- **`apm.lock.yaml` turning up modified is expected, not a bug.** kyberforge's `SessionStart` hook runs `apm outdated` at startup and `apm update --yes` when something is behind, which rewrites the lock. Commit or discard it deliberately.
+- **`apm.lock.yaml` turning up modified is expected, not a bug.** kyberforge's `SessionStart` hook keeps the install current on launch and rewrites the lock in the process (ADR-0019). Commit or discard it deliberately.
 - **A `.apm/` edit is not live in this session until it is pushed.** The six dependencies resolve from the holocron remote, unpinned against the default branch. `apm install` deploys from the lock; `apm update` is what re-resolves refs.
 - **No pre-push hook needs the network.** Root `apm.yml`'s marketplace has no remote package entries, so every hook resolves locally.
 - **This repo and Gitea are the only source of truth.** All project state, decisions, and working conventions live here. Do not use an external memory system for this project — cached state diverges from the repo and you get a split brain. Before answering any design or architecture question, check `docs/adr/` for an existing decision.