feat(warm_catalog_stats): retire sweep gate as default, compute hourly regardless

[WilfordGrimley]

Summary

Retires the 2026-07-29 sweep gate as the default behaviour per the owner's 2026-08-03 ruling (reverses the 2026-07-29 gate ruling). The gate was freezing the stats page indefinitely under the streaming micro-batch sweep design, where a RUNNING PilotRunLedger row is perpetually present.

What changed:

• WARM_CATALOG_STATS_SWEEP_GATE_ENABLED default: True → False
• Command now computes all five panels every hourly run by default, printing "sweep gate: disabled (default) — computing all five panels" so operators can see which mode ran from the log.
• The gate is preserved as an opt-in emergency lever: set WARM_CATALOG_STATS_SWEEP_GATE_ENABLED=true in the env to restore the 2026-07-29 skip behaviour.
• _find_blocking_sweep helper and staleness bound unchanged.

Three-part rationale (verified):

1. MVCC safety. The five aggregations are plain SELECT queries — they never block on or are blocked by the streaming sweep's tiny micro-batch INSERTs.
2. Sweep artifacts already filtered. runHistory filters slow-path rows (catalog_stats.py lines ~391–396), and the vote panels count only human sources (HUMAN_SOURCES = USER/ADMIN/FEDERATED), so mid-sweep numbers are stable and correct.
3. ~9s measured compute. Full compute of all five panels measures ~9s (last ungated run 2026-08-02T16:00:22Z → 16:00:31Z), trivial load once an hour.

Test plan

• python3 -m pytest MPCAutofill/cardpicker/tests/test_warm_catalog_stats.py -x -q — 5 passed, 0 failed
• python3 -m pytest MPCAutofill/cardpicker/tests/test_catalog_stats.py -x -q -k "not (TestSharedCacheNotConfigured or TestGetCatalogStatsView)" — 65 passed, 0 failed (2 pre-existing staticfiles-manifest failures excluded from scope)
• pre-commit run --files on all touched files — black, isort, ruff, mypy, prettier: all Passed
• CI — not watched by this session per dispatch convention

Tasks-end checks (catalog repo CLAUDE.md):

• wiki: docs/features/catalog-stats.md — the Sweep-gate section rewritten in place to describe the gate as OFF by default with opt-in re-enablement path.
• docs: docs/features/catalog-stats.md — updated in-place (this change). No other doc changes needed.
• extractable-primitives: none — this is a config default flip + command docstring update; snip no new primitive extracted or destroyed, no dependency on vote/consensus/auth.