Backfill Slack directory person cards

[mrubens]

What changed

• backfill Brain person cards from every human member returned by connected Slack workspace directories
• create standalone cards for Slack members without Roomote accounts and aliases for linked identities
• refresh linked profiles with users.info and include Slack display names, real names, and job titles
• cache a privacy-safe subset of directory profiles while excluding bots and app users from Brain pages
• document the behavior and extend the mock Slack API and collector tests

Why

Person cards previously came only from Roomote users and provider mappings. That omitted teammates who appear throughout Slack history but do not have Roomote accounts, and linked cards lacked useful profile context such as job titles.

Impact

After the collector backfills, agents can resolve people across Slack discussions using workspace names, handles, and titles. Email, status, timezone, and avatar fields are not retained or written to the Brain.

Validation

• BullMQ Brain collector tests (40 tests)
• Slack mock server tests (14 tests)
• pnpm lint:fast
• pnpm check-types:fast
• pnpm knip
• Drizzle migration check

[roomote-community]

No new code issues found. See task

• New Slack workspaces can be skipped for 24 hours because missing per-team state falls back to the global backfill timestamp.

_{Reviewed 1cdd9a6}