fix: route bot triggers from Discord threads

[vycdev2]

Summary

• Treat Discord threads as supported bot request channels alongside regular guild text channels.
• Keep existing message, reaction, live-context, typing, and response routing behavior unchanged for ordinary text channels.
• Add focused regression coverage for thread and non-message channel routing.

Verification

• node --test tests/discordChannelRouting.test.mjs — passed (2 tests)
• npm run build — passed
• node --input-type=module -e 'await import("node-pty")' — passed
• git diff --check and git diff --cached --check — passed
• git merge-base --is-ancestor upstream/main HEAD — passed
• npm test — 65/67 passed; two pre-existing timing-sensitive Claude auth force-kill tests failed in one full-suite run, and the auth file also reproduced one intermittent failure when run alone. The focused regression and build passed.
• No format script is configured in package.json.

Risk

• Low: the routing guard now accepts only TextChannel and ThreadChannel; DM and unrelated channel types remain excluded.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.