…navigation

Fixes the `@ci.job.url` tag to construct proper job-specific URLs that navigate
directly to the job logs instead of the commit checks page.

Core changes:
- Add `JOB_CHECK_RUN_ID` environment variable support for explicit job ID
- Implement diagnostics file parsing to extract numeric job ID from Worker_*.log
- Use dual extraction strategy: JSON parse with regex fallback for robustness
- Construct correct URL format: `{repo}/actions/runs/{run_id}/job/{job_id}`

Priority order for job ID resolution:
1. `JOB_CHECK_RUN_ID` environment variable (set via `${{ job.check_run_id }}`)
2. GitHub Actions runner diagnostics files (`_diag/Worker_*.log`)
3. Fallback to `GITHUB_JOB` with commit checks URL (existing behavior)

Defensive measures:
- 10MB file size limit for diagnostics files
- Graceful error handling with debug logging
- Platform-specific diagnostic directory detection (Linux, macOS, Windows)