feat: add api extractor, semantic diff, and sync workflow

[tharropoulos]

Change Summary

• add a typed C++ extractor that discovers routes, resolves parameters, and builds the API spec
  • split extraction into smaller runtime modules for config, source loading, traversal, resolution, and spec output
  • add a semantic-diff command to compare extracted specs and generate JSON/Markdown change reports
  • wire in GitHub Actions to run extraction, publish artifacts, and open follow-up issues when API shape changes

PR Checklist

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[tharropoulos]

@jasonbosco