feat: Playnite library sync plugin + exporter

A two-part Punktfunk plugin that syncs the Playnite library into the host
game library as the `playnite` provider:

- exporter/ — a minimal C# Playnite GenericPlugin ("Punktfunk Sync") that
  writes punktfunk-library.json on every library change. Reading Playnite's
  live-locked LiteDB from outside isn't robust, so this adapter runs inside
  Playnite. Builds net462 via reference assemblies; packaged as a .pext.
- src/ — the TS plugin (on @punktfunk/host, rom-manager shape): watches the
  export, embeds covers as data URLs, reconciles via
  PUT /library/provider/playnite, with a console-hosted web UI + standalone
  fallback + CLI. Launch = playnite://playnite/start/<id>, run by the host
  in the interactive session so Playnite performs the real launch.

Verified locally: backend tsc + 23 tests + biome clean, SPA build, C#
exporter build + .pext pack.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ui/package.json

@@ -0,0 +1,25 @@
+{
+	"name": "punktfunk-plugin-playnite-ui",
+	"private": true,
+	"type": "module",
+	"description": "The Playnite plugin SPA — built into ../dist/ui and served by servePluginUi. Self-contained (Tailwind + the Punktfunk brand tokens) so it builds with no design-system registry auth.",
+	"scripts": {
+		"dev": "vite",
+		"build": "vite build",
+		"typecheck": "tsc --noEmit"
+	},
+	"dependencies": {
+		"lucide-react": "^0.469.0",
+		"react": "^19.2.0",
+		"react-dom": "^19.2.0"
+	},
+	"devDependencies": {
+		"@tailwindcss/vite": "^4.3.2",
+		"@types/react": "^19.2.0",
+		"@types/react-dom": "^19.2.0",
+		"@vitejs/plugin-react": "^5.0.0",
+		"tailwindcss": "^4.3.2",
+		"typescript": "^5.9.3",
+		"vite": "^7.0.0"
+	}
+}