feat(kyberforge): enable codex marketplace output

Uncomment marketplace.outputs.codex in apm.yml. Codex output requires
every package to declare a category -- added one per package (Developer
Tools / Utilities / Version Control / Productivity, matching each
plugin's actual scope).

Re-running apm pack after enabling codex auto-synced 'codex' into each
local package's own targets: list (apm.yml, per plugin) -- packages
belonging to a marketplace that publishes a codex output need to declare
codex as a supported compile target for that to be coherent. Verified
idempotent: a second apm pack --check-clean run makes no further changes.

.claude-plugin/marketplace.json regenerated (now carries category per
plugin); .agents/plugins/marketplace.json is the new codex artifact.

Refs: #90

plugins/git/apm.yml

@@ -17,6 +17,7 @@ keywords:
 targets:
   - claude
   - copilot
+  - codex
 type: hybrid
 
 dependencies: