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>

bunfig.toml

@@ -0,0 +1,5 @@
+# Resolve the `@punktfunk` scope from the Gitea npm registry (like `@punktfunk/host` itself), so
+# `bun add @punktfunk/plugin-playnite` pulls the shared `@punktfunk/host` + `effect` deps out of the
+# box. During local development the SDK is consumed via `bun link @punktfunk/host`.
+[install.scopes]
+"@punktfunk" = "https://git.unom.io/api/packages/unom/npm/"