fix(kyberforge): bridge apm content to Claude Code's flat plugin discovery

Claude Code's (and Copilot's) native plugin installer has zero awareness of
.apm/ nesting -- it convention-scans only flat skills/, agents/, commands/,
hooks.json at each plugin's root. Confirmed via strings on the installed
claude binary and live installs of git@holocron/gitea@holocron/kyberforge@
holocron, all reporting Skills(0) Agents(0) Hooks(0) post ADR-0015's apm
conversion. Root cause (apm_cli/core/plugin_manifest.py): apm's plugin.json
compiler deliberately strips skills/agents/commands keys, assuming the host
already auto-discovers those convention directories -- it has no model of
.apm/ being host-visible at all. Separately, apm's own bundle exporter
(apm_cli/bundle/plugin_exporter.py, behind `apm pack --format plugin`)
implements the correct .apm/ -> flat mapping, but only ever targeted
build/<name>-<version>/, a path nothing in marketplace.json's source: points
at.

scripts/sync-plugin-content.sh wraps that bundle exporter and copies its
agents/, skills/, commands/, instructions/, extensions/, and merged
hooks.json back into each plugin's own root as a second tracked
compiled-output category -- same governance status as
.claude-plugin/plugin.json: generated from .apm/, never hand-edited. tests/
subdirectories are excluded from the mirror (dev fixtures, not host-visible
runtime content; several hardcode a relative repo-root walk-up sized for the
.apm/-nested depth, which breaks when duplicated one level shallower).
Applied for real across all 6 plugins and verified two ways: `claude plugin
validate --strict` passes on every real plugin directory, and a live
`claude --plugin-dir <path> -p "list skills/agents"` behavioral test
confirms content is now actually discovered.

Also, from the same issue #90 review round:
- scripts/check-manifests.sh pointed at each plugin's root-level plugin.json
  (checking skills/hooks/mcpServers/agents pointer fields) -- that file was a
  stale near-duplicate of .claude-plugin/plugin.json nothing else read or
  wrote, now deleted across all 6 plugins. check-manifests.sh is rewritten to
  validate .claude-plugin/plugin.json instead, and drops the pointer-field
  checks entirely (nothing to check -- those fields are correctly absent by
  design). Content-presence drift is now check-plugin-content-sync's job, a
  new pre-push hook wired in .pre-commit-config.yaml.

docs/adr/0017 records the root cause and decision in full, including two
rejected alternatives (patching plugin.json's path fields directly -- apm's
compiler strips them on every run; pointing marketplace.json at apm pack's
build/ output -- a version-suffixed non-source directory nothing can install
from without an extra build step). ADR-0015 and CONTEXT.md are updated to
point at it.

Refs: #90

plugins/kyberforge/skills/agent-audit/references/description-quality.md

@@ -0,0 +1,49 @@
+---
+source_keys:
+  - context7-websites-code-claude
+  - claude-code-plugins-docs
+  - claude-code-subagents-docs
+  - context7-github-en-copilot
+  - github-custom-agents-configuration
+---
+
+# Agent Description Quality Reference
+
+Load this file when a description finding is borderline and you need to make a precise call.
+
+## Action-verb opening
+
+The description must open with an imperative or present-tense verb that describes what the agent does ("Reviews...", "Audits...", "Generates...", "Analyzes..."). Avoid:
+- Noun phrases: "An agent that..." — no verb
+- "This agent..." or "Use this when..." — passive framing
+- "Helps with..." — too vague to be a clear verb
+
+**Borderline call:** "Validates and reviews..." is acceptable — two verbs is fine if both are specific. "Assists in reviewing..." is not — "assists" is vague filler.
+
+## Specificity of trigger condition
+
+The description must state what specifically triggers the agent. Generic phrasing fails:
+- Too vague: "when the user needs help with agents"
+- Acceptable: "when the user says 'audit this agent', 'check if my agent follows best practices', or wants to know if an agent pair is ready to ship"
+
+Include indirect triggers: "even if they don't use the word 'audit'" or "even if the user doesn't phrase it as a review request". If the agent should activate on a recognisable user goal (not just literal keyword matches), name that goal.
+
+**Borderline call:** If the description covers direct triggers but omits common indirect phrasings that a user would plausibly use, mark as SUGGESTION (not FAIL) — the agent still activates, just less reliably.
+
+## `Use proactively`
+
+For CC files: including "Use proactively" signals the CC runtime to offer the agent unprompted when conditions are met. This is CC-specific — use it when the agent should activate without an explicit user request.
+
+For Copilot files: this phrase has no effect. Use `user-invocable: false` / `disable-model-invocation: true` for equivalent Copilot behavior. Flag `Use proactively` in a Copilot description as a SUGGESTION (not FAIL) — it causes no harm, just has no effect.
+
+## Length and hard limits
+
+- CC agent descriptions: no documented character limit, but keep under 500 characters to avoid truncation in UI contexts.
+- Copilot agent descriptions: no separate documented limit, but the overall 30,000-character body limit applies to the full file.
+- Skill descriptions (SKILL.md): hard 1024-character limit enforced by the platform.
+
+## Do not use when
+
+Include a "Do not use when..." clause only if a near-miss agent or skill exists that could steal activations. Omitting it is not a finding. Including it is correct when there is a real confusion risk (e.g., `/agent-audit` vs `/skill-audit`).
+
+**Borderline call:** If the "Do not use when" clause is present but the exclusion described is already obvious from context, mark as SUGGESTION to tighten or remove — not FAIL.