Add discord channel plugin

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/.claude-plugin/plugin.json

@@ -0,0 +1,11 @@
+{
+  "name": "discord",
+  "description": "Discord channel for Claude Code \u2014 messaging bridge with built-in access control. Manage pairing, allowlists, and policy via /discord:access.",
+  "version": "0.0.1",
+  "keywords": [
+    "discord",
+    "messaging",
+    "channel",
+    "mcp"
+  ]
+}