feat: add iMessage channel, channels setup guide, 3-way distinction

- messaging/channels-setup.md: comprehensive guide covering all 3
  channels (Telegram, Discord, iMessage), bun install, plugin setup,
  session persistence workarounds, and enterprise admin settings
- messaging/imessage-setup.md: macOS-specific iMessage setup with
  Full Disk Access, /imessage access allow, and known quirks
- messaging/README.md: rewritten with 3-way distinction table
  (Channels=event-based, Dispatch=message-based, RC=direct control)
- examples/12: expanded from 2 options to 3 with clear trigger model
- feature-map.md: row 9 updated to include iMessage
- README.md: session persistence warning added as top-level section

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

messaging/imessage-setup.md

@@ -0,0 +1,94 @@
+# iMessage Channel Setup
+
+Send a text to your Claude Code session from iMessage. Claude
+reads it, executes with all your skills and tools, and texts
+back the result. Works with iMessage (blue bubbles) and SMS
+(green bubbles).
+
+**macOS only.** iMessage requires the Messages app on macOS.
+
+## Setup (5 minutes)
+
+### 1. Grant Full Disk Access
+
+System Settings > Privacy & Security > Full Disk Access >
+Add your terminal (Terminal.app, VS Code, iTerm2, etc.)
+
+This lets the plugin read the iMessage database.
+
+### 2. Install Bun
+
+```bash
+curl -fsSL https://bun.sh/install | bash
+```
+
+### 3. Install the iMessage plugin
+
+In a Claude Code session:
+```
+/install @anthropic-ai/claude-code-imessage
+```
+
+Verify: `/plugins` should show the iMessage plugin as connected.
+
+### 4. Launch with channels
+
+```bash
+claude --channels
+```
+
+You should see: `Listening for channel messages from plugin iMessage`
+
+### 5. Test it
+
+Send yourself an iMessage: "Hey, can you hear me?"
+
+Claude Code should receive the message and respond through
+iMessage.
+
+## Allow other phone numbers
+
+By default, only your own number/Apple ID is allowed. To let
+others text your Claude Code:
+
+```
+/imessage access allow +1234567890
+```
+
+Or allow by Apple ID:
+```
+/imessage access allow someone@icloud.com
+```
+
+The first time a new number texts, Claude Code will ask you
+to confirm before allowing access.
+
+## Known quirk: double messages
+
+If you text yourself, every message appears twice (once as
+sender, once as receiver). Fix: text from a different number
+or Apple ID, or use the `/imessage access allow` command to
+set up a separate contact.
+
+## Tips
+
+- **Bypass permissions for unattended use:**
+  `claude --channels --dangerously-skip-permissions`
+  (Only in trusted environments. Prefer Auto Mode instead.)
+
+- **Auto Mode for safer autonomy:**
+  `claude --channels --enable-auto-mode`
+
+- **Keep session alive:** Use `tmux` or `screen` so the session
+  survives if your terminal closes.
+
+- **Skills via iMessage:** Any skill you have configured works.
+  Text "Run /daily-briefing" and your agent executes it.
+
+## Limitations
+
+- macOS only (iMessage database is a macOS feature)
+- Session must be running (no daemon mode)
+- No end-to-end encryption awareness (messages are plain text
+  to the plugin)
+- Rate limiting: Claude Code processes one message at a time