docs: clean up stale TODO.md backlog

Remove completed items (username, dork, wayback, per-channel filtering,
message truncation, reconnect backoff, structured logging, bot/config
tests).

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

TODO.md

@@ -2,25 +2,16 @@
 
 ## Plugins
 
-- [ ] `username` -- cross-platform username enumeration
 - [ ] `emailcheck` -- SMTP VRFY/RCPT TO verification
-- [ ] `dork` -- Google dork query builder
-- [ ] `wayback` -- Wayback Machine snapshot lookup
 - [ ] `canary` -- canary token generator/tracker
 
 ## Bot Features
 
-- [ ] Per-channel plugin enable/disable
+- [ ] Multi-server support (per-server config, shared plugins)
-- [ ] Multi-server support
+- [ ] Stable plugin API (versioned, breaking change policy)
-- [ ] Stable plugin API (versioned)
-- [ ] Message truncation for IRC 512-byte limit
-- [ ] Configurable reconnect backoff (exponential)
-- [ ] Structured logging (JSON output option)
 
 ## Testing
 
 - [ ] Integration tests with mock IRC server
-- [ ] Bot orchestrator unit tests
-- [ ] Config merge edge case tests
 - [ ] Plugin command tests (encode, hash, dns, etc.)
 - [ ] CAP negotiation tests (mock connection)