/add-slack (#366)

* feat: add Slack channel skill (/add-slack)

Slack Bot integration via @slack/bolt with Socket Mode. Can replace
WhatsApp entirely (SLACK_ONLY=true) or run alongside it.

- SlackChannel implementing Channel interface (46 unit tests)
- Socket Mode connection (no public URL needed)
- @mention translation (Slack <@UBOTID> → TRIGGER_PATTERN)
- Message splitting at 4000-char Slack API limit
- Thread flattening (threaded replies delivered as channel messages)
- User name resolution with caching
- Outgoing message queue with flush-on-reconnect
- Channel metadata sync with pagination
- Proper Bolt types (GenericMessageEvent | BotMessageEvent)
- Multi-channel orchestrator changes (conditional channel creation)
- Setup guide (SLACK_SETUP.md) and known limitations documented

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

* local settings

* adjusted when installing

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/add-slack/modify/src/index.ts.intent.md

@@ -0,0 +1,60 @@
+# Intent: src/index.ts modifications
+
+## What changed
+Refactored from single WhatsApp channel to multi-channel architecture supporting Slack alongside WhatsApp.
+
+## Key sections
+
+### Imports (top of file)
+- Added: `SlackChannel` from `./channels/slack.js`
+- Added: `SLACK_ONLY` from `./config.js`
+- Added: `readEnvFile` from `./env.js`
+- Existing: `findChannel` from `./router.js` and `Channel` type from `./types.js` are already present
+
+### Module-level state
+- Kept: `let whatsapp: WhatsAppChannel` — still needed for `syncGroupMetadata` reference
+- Added: `let slack: SlackChannel | undefined` — direct reference for `syncChannelMetadata`
+- Kept: `const channels: Channel[] = []` — array of all active channels
+
+### processGroupMessages()
+- Uses `findChannel(channels, chatJid)` lookup (already exists in base)
+- Uses `channel.setTyping?.()` and `channel.sendMessage()` (already exists in base)
+
+### startMessageLoop()
+- Uses `findChannel(channels, chatJid)` per group (already exists in base)
+- Uses `channel.setTyping?.()` for typing indicators (already exists in base)
+
+### main()
+- Added: Reads Slack tokens via `readEnvFile()` to check if Slack is configured
+- Added: conditional WhatsApp creation (`if (!SLACK_ONLY)`)
+- Added: conditional Slack creation (`if (hasSlackTokens)`)
+- Changed: scheduler `sendMessage` uses `findChannel()` → `channel.sendMessage()`
+- Changed: IPC `syncGroupMetadata` syncs both WhatsApp and Slack metadata
+- Changed: IPC `sendMessage` uses `findChannel()` → `channel.sendMessage()`
+
+### Shutdown handler
+- Changed from `await whatsapp.disconnect()` to `for (const ch of channels) await ch.disconnect()`
+- Disconnects all active channels (WhatsApp, Slack, or any future channels) on SIGTERM/SIGINT
+
+## Invariants
+- All existing message processing logic (triggers, cursors, idle timers) is preserved
+- The `runAgent` function is completely unchanged
+- State management (loadState/saveState) is unchanged
+- Recovery logic is unchanged
+- Container runtime check is unchanged (ensureContainerSystemRunning)
+
+## Design decisions
+
+### Double readEnvFile for Slack tokens
+`main()` in index.ts reads `SLACK_BOT_TOKEN`/`SLACK_APP_TOKEN` via `readEnvFile()` to check
+whether Slack is configured (controls whether to instantiate SlackChannel). The SlackChannel
+constructor reads them again independently. This is intentional — index.ts needs to decide
+*whether* to create the channel, while SlackChannel needs the actual token values. Keeping
+both reads follows the security pattern of not passing secrets through intermediate variables.
+
+## Must-keep
+- The `escapeXml` and `formatMessages` re-exports
+- The `_setRegisteredGroups` test helper
+- The `isDirectRun` guard at bottom
+- All error handling and cursor rollback logic in processGroupMessages
+- The outgoing queue flush and reconnection logic (in each channel, not here)