fix(kyberforge): scope check-plugin-content-sync to sync-relevant paths

The pre-push hook ran a full `apm pack` + directory diff across every
plugin on every push (always_run: true), even for changes that could
never affect the sync (e.g. a README edit). Add a files: regex scoped
to what scripts/sync-plugin-content.sh actually consumes -- each
plugin's apm.yml, .mcp.json (read by reinject_mcp_servers), .apm/**
(the sync source), the flat mirror output dirs themselves (agents/,
skills/, commands/, instructions/, extensions/, hooks.json -- so a
direct edit to compiled output is still caught as drift), the
marketplace.json --all reads to build the plugin list, and the sync
script itself -- and drop always_run now that files: covers every
input path.

.pre-commit-config.yaml

@@ -69,7 +69,7 @@ repos:
         language: system
         stages: [pre-push]
         pass_filenames: false
-        always_run: true
+        files: '^(scripts/sync-plugin-content\.sh|\.claude-plugin/marketplace\.json|plugins/[^/]+/(apm\.yml|\.mcp\.json|hooks\.json|\.apm/|agents/|skills/|commands/|instructions/|extensions/))'
 
       - id: check-marketplace-mirror-sync
         name: Check marketplace mirror sync