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/vite.config.ts

@@ -0,0 +1,16 @@
+import tailwindcss from "@tailwindcss/vite";
+import react from "@vitejs/plugin-react";
+import { defineConfig } from "vite";
+
+// `base: "./"` (relative asset URLs) is the plugin-ui-surface contract: the SPA is mounted under
+// `/plugin-ui/playnite/` behind the console proxy. Built into `../dist/ui`, which `servePluginUi`'s
+// staticDir points at.
+export default defineConfig({
+	base: "./",
+	plugins: [react(), tailwindcss()],
+	build: {
+		outDir: "../dist/ui",
+		emptyOutDir: true,
+	},
+	server: { port: 5601 },
+});