docs: update docs for Teams integration

- USAGE.md: Teams Integration section (config, setup, compat matrix)
- CHEATSHEET.md: Teams config snippet
- API.md: TeamsBot and TeamsMessage reference
- README.md: Teams in features list
- ROADMAP.md: v2.1.0 milestone
- TODO.md/TASKS.md: Teams items

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

TODO.md

@@ -82,6 +82,16 @@ is preserved in git history for reference.
 - [x] `shorten` -- manual URL shortening
 - [x] `cron` -- scheduled bot commands on a timer
 
+## Teams
+
+- [x] Microsoft Teams adapter via outgoing webhooks
+- [x] TeamsBot + TeamsMessage (duck-typed with IRC Message)
+- [x] HMAC-SHA256 webhook validation
+- [x] Permission tiers via AAD object IDs
+- [ ] Adaptive Cards for richer formatting
+- [ ] Graph API integration for DMs
+- [ ] Teams event handlers (member join/leave)
+
 ## Testing
 
 - [x] Plugin command unit tests (encode, hash, dns, cidr, defang)