fix: filter cross-repo closing references in PR timeline query (#1041)

[alpurkan17]

Summary

_PR_TIMELINE_QUERY's closingIssuesReferences fragment emits only nodes { number } without repository qualification. When a PR closes a same-numbered issue in a different repository, find_solver_from_cross_references matches by issue number alone and can credit the wrong solver.

Fix mirrors the approach from PR #1020 on the timeline query:

• Add repository { nameWithOwner } to the closingIssuesReferences fragment in _PR_TIMELINE_QUERY
• Filter closing numbers by matching repository name in the parser

Validation

• uv run ruff check — clean
• uv run ruff format --check — clean
• uv run pyright — 0 errors

Closes #1041

[alpurkan17]

Hi maintainers, this is a small 1-file fix (+11/-2) for cross-repo closing references in PR timeline query (fixes #1041). Quick review would be appreciated — thanks!