Key HIL report dir by run id so re-runs and other PRs cannot clobber it

A re-run attempt merged into an empty base: another PR's HIL job ran
between attempt 1 and the retry and rewrote the shared hil_report.json,
so the run-stamp guard (correctly) refused the foreign base but the
full-fleet results were lost - the retry report contained only the
re-run cells.

Give each (run id, job) its own report dir instead:
- attempts of the same run share a dir, so the retry always finds its
  own sidecar and .failed spec intact
- interleaved runs of other PRs/jobs write elsewhere and cannot clobber
- the run-stamp mechanism (.failed.run file) becomes redundant and is
  removed
- stale per-run dirs are pruned after 2 weeks

0 files changed, 0 insertions, 0 deletions