plex: full nox module — client, tools and events (ADR 0044/0046)

Moves plex's API client and tools out of the shared hal sdk into the module,
so a Plex API change rebuilds only plex. Tools: status, search, sessions,
recently-added, refresh. And a real event design: it emits playback
started/stopped and item.added by watching the server, and consumes
module.*.download.completed to rescan so a downloader's fetch becomes a
visible item. Typechecks against the sdk; manifest parses with its emits/
consumes and broker own-secret.

Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF

modules/plex/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "@novox/module-plex",
+  "version": "0.1.0",
+  "description": "plex — media server. Its API client, tools and events live here (novox/hq ADR 0044).",
+  "type": "module",
+  "private": true,
+  "dependencies": {
+    "@novox/mesh-sdk": "^0.1.0"
+  },
+  "devDependencies": {
+    "@types/node": "^22.0.0",
+    "typescript": "^5.6.0"
+  }
+}