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/skill-audit/references/description-quality.md

@@ -0,0 +1,54 @@
+---
+source_keys:
+  - agentskills-spec
+  - agentskills-optimizing-descriptions
+---
+
+# Description Quality Reference
+
+Source: agentskills.io — optimizing-descriptions
+
+## How triggering works
+
+At startup, agents load only the `name` and `description` of each skill. When a user's task matches a description, the agent reads the full `SKILL.md` into context. **The description carries the entire triggering burden** — the body is never seen until after triggering.
+
+Agents typically consult skills only for tasks requiring knowledge beyond their defaults. Specialized knowledge — unfamiliar APIs, domain-specific workflows, uncommon formats — is where description wording makes the difference.
+
+## What a good description does
+
+- **Imperative phrasing** — "Use when..." not "This skill does...". The agent is deciding whether to act.
+- **User intent, not mechanics** — describe what the user is trying to achieve, not how the skill works internally.
+- **Err toward being pushy** — explicitly name contexts where the skill applies, including cases where the user doesn't name the domain: "even if they don't mention X explicitly."
+- **Specificity over vagueness** — "parses and validates OpenAPI specs" beats "helps with APIs."
+- **Near-miss exclusions** — add "Do not use when..." only if a near-miss skill exists that could steal activations. Use strong near-misses (queries that share keywords but need something different), not weak ones ("write a fibonacci function").
+- **Hard limit: 1024 characters** — descriptions grow during revision; check length before finalising.
+
+## Before / after
+
+```yaml
+# Weak
+description: Process CSV files.
+
+# Strong
+description: >
+  Analyze CSV and tabular data files — compute summary statistics,
+  add derived columns, generate charts, and clean messy data. Use when
+  the user has a CSV, TSV, or Excel file and wants to explore, transform,
+  or visualize the data, even if they don't explicitly mention "CSV" or
+  "analysis."
+```
+
+The strong version names capabilities precisely and broadens applicability beyond explicit keyword matches.
+
+## Auditing guidance
+
+Flag as FAIL if:
+- Phrasing is descriptive ("This skill...") not imperative ("Use when...")
+- Capabilities are vague ("helps with APIs") — require precise verbs and nouns
+- No indirect trigger coverage when indirect cases clearly exist
+- No near-miss exclusions when a sibling skill could plausibly steal activations
+- Length exceeds 1024 characters
+
+Flag as SUGGESTION if:
+- Indirect trigger coverage exists but could be more specific
+- Near-miss exclusions are present but target weak near-misses only