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/git/skills/git-commits/references/commit-template.md

@@ -0,0 +1,66 @@
+---
+source_keys:
+  - org-commit-conventions
+---
+
+# Commit Message Body Template
+
+Use this structure for the body/footer of any non-trivial commit (skip sections that don't apply — do not leave placeholders in the actual commit).
+
+```
+<type>(<scope>): <concise summary>
+```
+The header is required. Describe the intended outcome, not the implementation.
+
+## Why
+
+Explain why this change exists. This is the most valuable part of the commit — the diff already shows *what* changed; future maintainers (human or AI) need *why*.
+
+Include, where applicable:
+- Problem being solved
+- User or business need
+- Bug or root cause
+- Important context not visible in the code
+
+Omit if the reason is immediately obvious.
+
+## Implementation Notes
+
+Capture decisions that are difficult to infer from the code:
+- Why this approach was chosen
+- Important assumptions or invariants
+- Constraints imposed by external systems
+- Tradeoffs or intentional compromises
+- Non-obvious implementation details
+- Workarounds or temporary solutions
+
+Do NOT describe the diff ("renamed X", "added Y"). Omit if there's nothing worth preserving.
+
+## Impact
+
+Document effects future developers should know about:
+- Behavior changes
+- Breaking changes
+- Performance implications
+- Security considerations
+- Migration or deployment requirements
+- Compatibility concerns
+- Follow-up work or known limitations
+
+Omit if there are no noteworthy impacts.
+
+## Trailers
+
+Structured metadata for traceability and tooling. Use only the trailers that apply:
+
+```
+Fixes:
+Refs:
+ADR:
+RFC:
+Design:
+Co-authored-by:
+Reviewed-by:
+Signed-off-by:
+BREAKING CHANGE:
+```