Add telegram channel plugin (#735)

Telegram messaging bridge for Claude Code. Runs a local MCP server that
connects to the Telegram Bot API via a user-created bot token.

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

Ships full source — server.ts runs locally via bun, started by the
.mcp.json command. First external_plugins entry to bundle source rather
than point at a hosted MCP endpoint.

external_plugins/telegram/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "claude-channel-telegram",
+  "version": "0.0.1",
+  "license": "Apache-2.0",
+  "type": "module",
+  "bin": "./server.ts",
+  "scripts": {
+    "start": "bun install --no-summary && bun server.ts"
+  },
+  "dependencies": {
+    "@modelcontextprotocol/sdk": "^1.0.0",
+    "grammy": "^1.21.0"
+  }
+}