Add imessage channel plugin

iMessage bridge for Claude Code. Reads ~/Library/Messages/chat.db
directly for history and new-message polling; sends via AppleScript
to Messages.app. macOS only.

Built-in access control: inbound messages are gated by an allowlist
(default: self-chat only), outbound sends are scoped to the same
allowlist. The /imessage:access skill manages allowlists and policy.

Requires Full Disk Access and Automation TCC grants — both prompted
by macOS on first use.

Ships full source — server.ts runs locally via bun, started by the
.mcp.json command.

external_plugins/imessage/.claude-plugin/plugin.json

@@ -0,0 +1,11 @@
+{
+  "name": "imessage",
+  "description": "iMessage channel for Claude Code \u2014 reads chat.db directly, sends via AppleScript. Built-in access control; manage pairing, allowlists, and policy via /imessage:access.",
+  "version": "0.0.1",
+  "keywords": [
+    "imessage",
+    "messaging",
+    "channel",
+    "mcp"
+  ]
+}