[Fix] Accelerate and repair Brain backfills

[mrubens]

What changed

• continue bounded historical collector passes while they make progress, while preserving the 15-minute steady-state poll
• stop fast continuation on Brain backpressure and persist collector cursors after each landed batch
• make pull-request fact ingestion use a durable timestamp-plus-ID keyset
• reset collector checkpoints and requeue completed task memories when gbrain OAuth clients are provisioned after a corpus rebuild
• add a one-time state repair migration for deployments already affected
• replay task memories newest-first

This includes the newest-first task replay from #1356.

Why

Roomote stored collector watermarks in its application database while gbrain corpus data lived separately. Rebuilding the Brain could therefore leave Roomote believing task and integration backfills were complete, producing an almost-empty corpus. Historical integrations also waited up to 15 minutes between bounded batches even when more work was immediately available.

Impact

A fresh or rebuilt Brain repopulates its historical task, Slack, Granola, GitHub issue, and pull-request context promptly. Per-pass limits and typed backpressure remain, normal steady-state polling does not become more aggressive, and recent task history becomes useful first.

Validation

• focused BullMQ tests: 44 passed
• focused real-database Brain tests: 14 passed
• package typechecks for @roomote/db, @roomote/sdk, and @roomote/bullmq
• repository pre-push checks, targeted lint, and formatting

[roomote-community]

No new code issues found. See task

• Fast continuation also runs all incremental integration polls every second (apps/bullmq/src/scheduled-jobs/brain-outbox-drain.ts:315).
• PR-fact Brain backpressure is swallowed and can be retried every second during another backfill (apps/bullmq/src/scheduled-jobs/brain-outbox-drain.ts:612).
• PR-fact keyset cursor can permanently skip rows written at its current timestamp (apps/bullmq/src/scheduled-jobs/brain-outbox-drain.ts:634).

_{Reviewed f12751f}