feat(prd-1): implement M4a - Forgejo REST data fetching (PR/issue basics)
- Add src/forgejo/data/fetcher.ts: REST-based data fetcher replacing
GraphQL queries with parallel Octokit REST calls (PR details + files
+ commits via Promise.all, issue details, file status mapping, SHA
computation, TOCTOU title/body protection, user display name)
- Add test/forgejo-data-fetcher.test.ts with 31 test cases covering
field mapping, parallel fetch, null handling, and edge cases
- Output matches FetchDataResult type for downstream compatibility
- Comments/reviews left empty (M4b scope)
Progress: 33% complete (M1, M2, M4a done) - next: M4b or M5
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
