feat(actor-classifier): wire registerBotId() boot call for KNOWN_BOT_IDS

[optemism]

Context

PR #104 (refactor-actor-classifier) exports registerBotId(id) and makes KNOWN_BOT_IDS private, which is the safe API shape. However, nothing calls registerBotId() at boot, so the Set stays empty at runtime and bot detection via KNOWN_BOT_IDS never fires.

What's needed

1. Decide the source of truth for integration/bot IDs to register — options:

   • Hardcoded list in config (simplest — IDs rarely change)
   • Notion DB property (fetched at startup)
   • Environment variable

2. Add a boot call (e.g., in src/config.js or app entry) that calls registerBotId() for each known bot ID.

3. Add a test that verifies the boot call populates the Set correctly.

Why it matters (P1)

Without boot wiring, a Notion integration that presses a button and has a source.user_id present but no source.type: 'bot' will be classified as a person (mentionable: true), generating spurious Notion mention notifications.

Related

• PR refactor: unify webhook actor classification behind classifyWebhookActor #104: fix(review): auto-resolve R2-R8
• Plan: docs/plans/2026-04-29-002-refactor-webhook-actor-classification-plan.md

[optemism]

@LeSphax could you take a look at this please