Automate E2E timing matrix repair

[bcorfman]

What changed

• Automatically resolve a PR or Actions run and download every GitHub Actions artifact with gh run download.
• Discover and merge all Playwright shard reports, including the embedded HTML report format and newer files JSON shape.
• Add e2e-timing-repair to feed hard-ceiling timing failures into the existing bounded diagnosis/implementation/verification flow.
• Add explicit --publish support for a clean-checkout commit, push, and draft PR.

Validation

• 11 repair-harness test files passed (54 tests).
• TypeScript compilation passed.
• Validated artifact download and shard merge against Actions run 30495912652 (8 shards, 396 test attempts, 58 hard-ceiling failures).
• Safe /bin/false agent simulation reached the diagnosis gate without modifying product files.

Warnings between 7 and 10 seconds remain diagnostic-only; only tests over 10 seconds are eligible for repair.