Fix stage_e_shakedown run_id collision on same-day invocations

[WilfordGrimley]

Description

Fixes a drill-found defect in the #465 stage_e_shakedown spec's run_id convention (§7(b) dispatcher-kill drill) — not an implementation bug in PR #467, a defect in the spec's own run_id shape that PR carried out faithfully.

The prefix stage-e-shakedown-b<batchsize>-<date>-<batch-num> (date-only) collides with PilotRunLedger.run_id's UNIQUE constraint on any second same-day invocation of the driver: kill-and-resume (the command's own documented resume contract via --reextracted-after) and every multi-invocation wave die with IntegrityError at the very first batch's ledger create.

Fixed by including a microsecond-precision invocation timestamp (%Y%m%dT%H%M%S%f), mirroring dispatch_micro_batch's own default run_id convention (stage_e_dispatch.py's f"stage-e-stream-{timezone.now().strftime('%Y%m%dT%H%M%S%f')}Z") — every invocation now gets a distinct prefix while the b<batchsize> segment stays greppable for the #463 wave analysis.

Updated: the run_id-shape test (now a regex match, since the timestamp is no longer a fixed 8-digit date), a new test proving two same-day invocations produce disjoint run_id sets, the command's own module docstring, and the "Ledger convention" example in docs/features/stage-e-operations.md's "Shakedown driver" subsection (no other literal run_id example found elsewhere in that doc).

Checklist

• I have installed pre-commit and installed the hooks with pre-commit install before creating any commits.
• I have updated any related tests for code I modified or added new tests where appropriate.
• I have manually tested my changes as follows:
  • cd MPCAutofill && pytest cardpicker/tests/test_stage_e_shakedown.py cardpicker/tests/test_stage_e_dispatch.py -q — 71 passed (ran against a /tmp/mpcvenv venv, system Python lacks Django/deps). ruff/black/isort/mypy/prettier all pass via the pre-commit hook on the commit.
  • docs_lint.py clean.
• I have updated any relevant documentation or created new documentation where appropriate.