fix: bound status.json push retries by wall-clock deadline

[cgoea]

Motivation

Replace the fixed-attempt-count loop in update_status_json with a wall-clock deadline (QUARTZ_STATUS_PUSH_MAX_WAIT_SEC, default 15 minutes): each attempt still fetches and hard-resets onto fresh upstream before reapplying and pushing, exactly as before, but the loop now runs until the deadline elapses rather than a capped attempt count.

A large release fan-out has dozens of runs pushing to the same status.json ref within a minute or two. _max_retries capped that at a fixed number of attempts (12, each backing off up to BACKOFF_CAP_SEC), so a run that kept losing the push race for long enough would exhaust its budget, permanently dropping its update.

Technical Details

• After a backoff sleep, the loop re-checks the deadline and breaks early rather than starting an attempt it doesn't have time budget left to meaningfully retry from.
• Log messages and the final RuntimeError on deadline exhaustion now report elapsed attempts and wall-clock time (e.g. "Failed to push status.json after {attempt} attempts over {max_wait_seconds:.0f}s (deadline exceeded)") instead of attempt/max_retries.
• BACKOFF_BASE_SEC / BACKOFF_CAP_SEC / INITIAL_JITTER_SEC tuning values are left untouched -- this PR only changes the retry loop's stopping condition, not its backoff shape.

Test Plan

• Updated test_max_retries_env_override / test_max_retries_invalid_env_falls_back → test_max_wait_seconds_env_override / test_max_wait_seconds_invalid_env_falls_back to cover _max_wait_seconds()'s env var parsing/validation/fallback behavior.
• Added test_update_status_json_retries_until_deadline_then_raises: with _max_wait_seconds patched to a tiny deadline and _commit_and_push always returning RETRY, asserts update_status_json keeps retrying until the deadline elapses and then raises RuntimeError matching "deadline exceeded".
• Added test_update_status_json_succeeds_after_transient_retries: with _commit_and_push returning RETRY, RETRY, DONE, asserts the loop retries past transient race losses and returns the written status path on eventual success.

Test Result

• Ran the full scripts/receive_therock/tests/ suite to confirm no other tests assumed a fixed attempt count.