[codex] add partial job update endpoint

[TheGreatAion]

Summary

• expose PATCH /api/jobs/:id through the jobs router
• validate partial edits with the existing updateJobSchema
• update the in-memory record while preserving its server-owned id
• return a clear 404 response for unknown job ids
• add focused route-level regression coverage

Why

The API already exported updateJobSchema, but there was no route, controller path, or service method that let clients apply partial job edits.

Closes #3299

/claim #743

Demo

• Watch the short API demo video

The video runs real requests against the patched local API: create a job, apply a partial edit while preserving the server id, then request an unknown job and receive a 404.

Verification

• node --test src/tests/health.test.js src/tests/job-update.test.js from apps/api passes: 3 tests
• npm test remains blocked by the pre-existing node --test src/tests directory-argument issue tracked in API test script should discover test files instead of loading test directory #2014