Handle absolute temp paths in ignorePaths

[sentry-junior]

A workflow run failed while processing an ignore path with:

• failed to process ignore for /home/runner/work/_temp/2026-05-05T150243Z.json/2026-05-05T150243Z.json, skipping: path should be a path.relative()d string, but got "/home/runner/work/_temp/2026-05-05T150243Z.json/2026-05-05T150243Z.json"
• The failing path is in GitHub Actions runner temp space, not the repository checkout.
• Current evidence suggests Warden is passing an absolute temp path into ignore handling that expects repo-relative paths. Confidence: medium.
• Related repo evidence: src/action/workflow/schedule.ts forwards resolved.filters?.ignorePaths, and src/cli/files.ts computes repo-relative paths before invoking ignore matching.
• There may be a code path where temp-generated files bypass that normalization.

Reported by Geoff Goldsmith.
Action taken on behalf of David Cramer.