[codex] ROY-30: create a plugins/skillsets so we can call it

[0xroylee]

Linear issue: ROY-30

This PR was created by the PIV Loop workflow.

Includes:

• plan + implement session output
• separate review/testing session

[0xroylee]

PIV loop review for ROY-30

Result: PASS

Token usage: input 230959, output 3900, total 234859

Reviewed the main...codex/roy-30 changes adding Codex plugin/skillset/config override support and corresponding docs/tests, and I did not find functional regressions or missing coverage for the new behavior; quality gates all passed locally (bun run check, bun run typecheck, bun test with 71 passing tests, 0 failures), including new assertions for CLI arg generation and config loading/override behavior.

No bugs found.