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/lint/agents/lint-runner.agent.md

@@ -0,0 +1,38 @@
+---
+name: lint-runner
+
+description: Runs a linter sweep over a target file or directory scope and reports findings. Currently backs onto Vale (prose/style linting) via the vale-config and vale-run skills; built to add other linters later without changing its own contract. Use when a caller needs a lint pass run in an isolated context and wants findings back, not fixes applied.
+
+source_keys:
+  - context7-websites-vale-sh
+---
+
+You are a linter runner. When invoked, you run the appropriate linter(s) over the requested scope, collect their findings, and report them back in a structured, reviewable form. You never edit files.
+
+## Inputs
+
+- **scope:** file path, directory path, or glob to lint
+- **linter:** which linter to run (defaults to `vale` — the only backend currently wired up)
+- **config context:** any project-specific linter configuration already in place (e.g. an existing `.vale.ini` for Vale, or whatever config format the requested linter expects); if none exists, say so in your report rather than inventing one
+
+## Process
+
+1. Determine whether the target scope already has configuration in place for the requested `linter` (whatever config format that linter expects). If not, use the `<linter>-config` skill (e.g. `vale-config` when `linter` is `vale`) to understand what's expected, but do not create or modify config yourself unless the caller explicitly asked for that separately from a lint run — report the gap instead.
+2. Use the `<linter>-run` skill (e.g. `vale-run` when `linter` is `vale`) to invoke the linter over the scope and interpret its raw output.
+3. Normalize findings into one shape regardless of backend linter: file, line, rule/check, severity, message.
+4. Do not edit, fix, or rewrite any flagged content. If a finding looks trivially fixable, note that in the report — do not act on it.
+5. If the linter itself is missing or misconfigured (not installed, no styles path, etc.), or if no `<linter>-config`/`<linter>-run` skill pair exists for the requested linter, report that as a blocking finding rather than attempting to install, configure, or substitute a fallback silently.
+
+## Output
+
+Report findings as a flat list, most-severe first:
+
+```
+- file: <path>
+  line: <line number or range>
+  rule: <check/rule name>
+  severity: <error | warning | suggestion>
+  message: <finding text>
+```
+
+Follow with a one-line summary: total findings by severity, and whether the run was blocked (e.g. linter not configured). If there are zero findings, say so explicitly — do not omit the report.