Fix sibling GitHub Actions job scopes

[floze-the-genius]

Summary

• leave the current job context when indentation returns to the jobs mapping level
• let expect-jobs classify every sibling job identifier consistently
• add a regression assertion for the existing second job fixture

Fixes #51.

Tests

• Sublime syntax test build 4205 with default Packages master and PowerShell master (focused GitHub Actions package): pass
• Sublime syntax test build 4200 with default Packages v4200 and PowerShell st4107-5.1.1 (focused GitHub Actions package): pass
• git diff --check: pass

The all-package local Docker invocation also reached and passed the changed GitHub Actions test; unrelated existing Drone/Kong assertions were not used as the change gate because the ad hoc runner did not resolve Kong's source.yaml.sublime.syntax dependency. The repository's scheduled upstream workflow is green, and PR CI remains the authoritative full-suite result.

Disclosure

OpenAI Codex was used to investigate, implement, and test this change. The commit includes a DCO sign-off.

[keith-hall]

Thanks