refactor: restructure add-gmail skill for new skill architecture

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

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

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+# Intent: src/index.ts modifications
+
+## What changed
+
+Added Gmail as a channel option alongside WhatsApp (and any other channels).
+
+## Key sections
+
+### Imports (top of file)
+
+- Added: `GmailChannel` from `./channels/gmail.js`
+- Added: `GMAIL_CHANNEL_ENABLED` from `./config.js`
+
+### main()
+
+- Added: conditional Gmail channel creation after WhatsApp:
+  ```
+  if (GMAIL_CHANNEL_ENABLED) {
+    const gmail = new GmailChannel(channelOpts);
+    channels.push(gmail);
+    await gmail.connect();
+  }
+  ```
+- Gmail uses the same `channelOpts` callbacks as other channels
+- Incoming emails are delivered to the main group (agent decides how to respond, user can configure)
+
+## 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
+- WhatsApp and any other channel creation is untouched
+- Shutdown iterates `channels` array (Gmail is included automatically)
+
+## 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