Add discord channel plugin (#736)

Discord messaging bridge for Claude Code. Runs a local MCP server that
connects to Discord's Gateway 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.
Guild channels require opt-in and @mention. The /discord:access skill
manages pairing, allowlists, and policy.

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

external_plugins/discord/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "claude-channel-discord",
+  "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",
+    "discord.js": "^14.14.0"
+  }
+}