chore: drop the flat content mirror and native install support (ADR-0024)

apm becomes the only supported install path. The flat mirror at each plugin
root existed solely so Claude Code's native `claude plugin install` could
convention-scan plugin content (ADR-0017). With no native consumers, it cost
~20,000 tracked lines plus ~2,100 lines of sync tooling and ~88s of every
push to guard content apm never reads — and its only automated gate,
`claude plugin validate --strict`, passes on a plugin with zero content, so
it could not detect the defect ADR-0017 was created to fix.

Removes the mirror (213 files), the six per-plugin manifest pairs,
sync-plugin-content.sh, its 1,289-line test, the orphaned
marketplace-plugins.sh, and the check-plugin-content-sync and
validate-plugins pre-push hooks. The root `marketplace:` block and
.claude-plugin/ catalogue stay: apm's own marketplace consumers read that
same file, so `<name>@holocron` short names keep working.

tests/run-bats.sh now excludes .claude/skills/. apm installs from .apm/,
which carries the tests/ dirs the mirror stripped, so deployed .bats files
would otherwise be discovered and double-run.

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

docs/spec/architecture.md

@@ -19,13 +19,13 @@ project repo (local overrides)
 - **Executables** (`DEPLOY_EXECUTABLES`): `providers/claude-code/statusline-command.sh` → `~/.claude/statusline-command.sh` (with `+x`)
 - **Directories** (`DEPLOY_DIRS`): `core/` → `~/.claude/core/` (destination fully replaced on each deploy)
 
-Skills are **not** deployed by `install.sh`. They are distributed as plugins and installed separately — in this repo by `apm install` against the `dependencies.apm` entries in the root `apm.yml`, which lands them in `.claude/skills/` and `.claude/agents/` (ADR-0018); elsewhere by `claude plugin install <name>@holocron`.
+Skills are **not** deployed by `install.sh`. They are distributed as plugins and installed separately — in this repo by `apm install` against the `dependencies.apm` entries in the root `apm.yml`, which lands them in `.claude/skills/` and `.claude/agents/` (ADR-0018). A consuming repo installs them the same way — apm is the only supported install path.
 
 `~/.claude/CLAUDE.md` is a thin adapter, not a content source. It imports `~/.agents/AGENTS.md` (always-on rules) and `governance.md` (always-on governance) and carries nothing else — the content index of on-demand instruction files sits in `core/AGENTS.md`, deployed to `~/.agents/AGENTS.md` and imported by it. All always-on content lives in `AGENTS.md` files so other providers can import the same source without duplication.
 
 ## Plugin model
 
-Skills, agents, MCP servers, and hooks are distributed as self-contained plugin units under `plugins/`, installed independently — via `apm install` here, or `claude plugin install <name>@holocron` for a host consuming the marketplace natively (ADR-0018). Self-contained is a hard constraint, not a description: a plugin is copied to a cache on install, so nothing inside it may reference a file outside its own directory. That is why the Vale styles are duplicated across two skills rather than shared (ADR-0014), and why ADR-0020's constants are copied into three validators rather than sourced from one. Each plugin is an **apm package**: `plugins/<name>/apm.yml` plus a hand-authored `plugins/<name>/.apm/{skills,agents,hooks,commands,instructions,extensions}/` tree (ADR-0015). There is no hand-maintained `plugin.json` — every manifest and every host-visible content directory is compiled from that source.
+Skills, agents, MCP servers, and hooks are distributed as self-contained plugin units under `plugins/`, installed independently via `apm install`, here and in any consuming repo (ADR-0018). Self-contained is a hard constraint, not a description: a plugin is copied to a cache on install, so nothing inside it may reference a file outside its own directory. That is why the Vale styles are duplicated across two skills rather than shared (ADR-0014), and why ADR-0020's constants are copied into three validators rather than sourced from one. Each plugin is an **apm package**: `plugins/<name>/apm.yml` plus a hand-authored `plugins/<name>/.apm/{skills,agents,hooks,commands,instructions,extensions}/` tree (ADR-0015). There is no per-plugin `plugin.json` at all — apm reads `apm.yml`, and the repo's one generated manifest, `.claude-plugin/marketplace.json`, is compiled from that source.
 
 Which plugin a new skill belongs in follows from what each one is scoped to. The boundary that matters most in practice is `core` vs `kyberforge`: `core` is the home for cross-cutting, repo-agnostic utility skills that a consumer would want against *their* repo, while `kyberforge` is meta-tooling for the holocron marketplace itself. A skill that authors a target repo's `AGENTS.md` is `core`; a skill that audits a `SKILL.md` against this marketplace's contract is `kyberforge`.
 
@@ -42,14 +42,15 @@ These are routing boundaries, not inventories — they answer "where does a new
 | `lint` | Configuring and running linters against a target repo; repo-agnostic, first linter is Vale |
 | `bin` | Unsorted skills that have not earned a home yet |
 
-Two compilers produce the plugin roots you see in the tree:
+One compiler produces the generated content in the tree:
 
-- **`apm pack` compiles the manifests** (ADR-0015). Per plugin: `.claude-plugin/plugin.json` and `.github/plugin/plugin.json`, both generated from `plugins/<name>/apm.yml`. Repo-wide, from the root `apm.yml`'s `marketplace:` block: `.claude-plugin/marketplace.json` (apm's `claude` output profile) — the only marketplace manifest this repo generates or ships. Copilot CLI checks for a marketplace manifest at several conventional paths, falling back through `.github/plugin/marketplace.json` to `.claude-plugin/marketplace.json` — since this repo already generates the latter, no dedicated Copilot-path mirror is maintained.
-- **`scripts/sync-plugin-content.sh` compiles the content mirror** (ADR-0017). It wraps `apm pack --format plugin` and copies the resulting bundle's flat `agents/`, `skills/`, `commands/`, `instructions/`, `extensions/`, and merged `hooks/hooks.json` back to the plugin root. Claude Code's installer convention-scans those flat paths and has no `.apm/` awareness whatsoever, so the mirror exists solely to satisfy the host's discovery contract.
+- **`apm pack` compiles the marketplace manifest** (ADR-0015). Repo-wide, from the root `apm.yml`'s `marketplace:` block: `.claude-plugin/marketplace.json` (apm's `claude` output profile) — the only manifest this repo generates or ships. Copilot CLI checks for a marketplace manifest at several conventional paths, falling back through `.github/plugin/marketplace.json` to `.claude-plugin/marketplace.json` — since this repo already generates the latter, no dedicated Copilot-path mirror is maintained.
 
-`.apm/` is the sole hand-edited authoring source for plugin content. An edit made in the flat mirror is discarded by the next sync and is reported as drift by the `check-plugin-content-sync` pre-push hook. Hand-authored material that is not an `.apm/` primitive — `README.md`, `docs/`, `bin/`, `sources.md`, `.mcp.json`, and per-plugin extras such as `plugins/gitea/references/` and `plugins/bin/evals/` — lives at the plugin **root** and is untouched by either compiler.
+apm is the only supported install path. A flat `skills/`, `agents/`, `hooks/` mirror used to be compiled to each plugin root so Claude Code's installer could convention-scan it, alongside a per-plugin `.claude-plugin/plugin.json` and `.github/plugin/plugin.json`; both are gone, together with native `claude plugin install` support. apm reads `plugins/<name>/apm.yml` and deploys from `.apm/` directly, and never probed those manifests.
 
-That immunity is positional, not by filename. Anything placed *inside* a mirrored directory is destroyed regardless of what it is: `sync_dir` runs `rm -rf "$dst"` before every copy, and `sync_hooks_json` does the same to `hooks/`. A hand-written `README.md` under `plugins/<name>/hooks/` or `plugins/<name>/skills/` is deleted by the next sync with no drift report, because a file with no `.apm/` counterpart is simply absent from the regenerated tree. This has already cost the repo one document — `plugins/kyberforge/hooks/README.md`, since restored to `plugins/kyberforge/docs/hooks.md`. Plugin-root documentation belongs in `docs/`.
+`.apm/` is the sole hand-edited authoring source for plugin content. Hand-authored material that is not an `.apm/` primitive — `README.md`, `docs/`, `bin/`, `sources.md`, `.mcp.json`, and per-plugin extras such as `plugins/gitea/references/` and `plugins/bin/evals/` — lives at the plugin **root**. A hand-edit to the generated `.claude-plugin/marketplace.json` is reported as drift by the `apm-pack-check-clean` pre-push hook.
+
+Plugin-root documentation belongs in `docs/`. That convention is older than the mirror's removal: a hand-written `README.md` placed inside a mirrored directory used to be destroyed by the next sync with no drift report, which cost the repo one document — `plugins/kyberforge/hooks/README.md`, since restored to `plugins/kyberforge/docs/hooks.md`.
 
 ## Governance layer