refactor: rewrite on @punktfunk/plugin-kit — contract + plugin workspaces

The framework half of this plugin (engine lifecycle, config/state, host
reconcile, UI server, CLI) was ~80% identical to rom-manager's. That code is
now @punktfunk/plugin-kit; this replaces the local copy with it and adopts the
rom-manager blueprint layout.

  contract/  Effect Schemas: the cross-process export contract (the C#
             exporter's other half, with the schema-version guard as a decode
             check), the config schema (one schema, Encoded = authored file
             shape, defaults only via withDecodingDefaultKey), domain DTOs, the
             HttpApi contract, API errors.
  plugin/    src/domain = the pure core (locate/read, art, reconcile), ported
             tests green before any Effect wiring; src/services = the kit's
             ConfigService/CacheStore/SyncEngine/ProviderClient; definePluginKit
             entry, kit CLI, auth-free dev API.

Preserved, because they are what makes playnite work at all: the ingest inbox
is still read FIRST (the de-privileged LocalService runner cannot reach the
interactive user's %APPDATA%), the host/dataurl/off art modes, and the
playnite:// launch hand-back. The C# exporter is untouched.

New: per-game include/exclude overrides, and an allow-listed /api/art proxy so
the SPA can render local Playnite covers — it serves only paths the currently
ingested export references.

Dropped: the standalone password UI server (console surface + CLI only, as in
rom-manager 0.3.0) and the devEntry flag.

Trap found and fixed here: the HttpApi encoder serialises `undefined` as
`null`, so a `Schema.optional` field the server omits cannot be decoded by the
client — silently in the SSE feed, loudly in the typed client. Every optional
EngineStatus field is `Schema.NullOr` with an explicit value on the wire.

contract/src/domain.ts

@@ -0,0 +1,88 @@
+// Domain DTOs shared by the plugin server and the UI — Schemas are the source of truth,
+// the derived types keep the original domain names so the pure core reads unchanged.
+//
+// Trap, measured on this API (rom-manager's note only covers half of it): `optionalKey`
+// rejects a present-but-`undefined` value and 400s at the RESPONSE encoder — but
+// `Schema.optional` is not the fix, because the HttpApi encoder serialises `undefined` as
+// `null`, and `string | undefined` then refuses that null when the CLIENT decodes it. The
+// failure is silent in the SSE feed (invalid frames are skipped) and loud in the typed
+// client. So: every "may be absent" field here is `Schema.NullOr`, and the server always
+// sends an explicit value. JSON-native, symmetric, no undefined anywhere on the wire.
+import { Schema } from "effect";
+
+/** Where the export was found — drives the console's "exporter connected?" banner. */
+export const Location = Schema.Struct({
+	/** The resolved source dir (the ingest inbox, or a Playnite data dir), or null. */
+	dir: Schema.NullOr(Schema.String),
+	/** Every dir considered, in probe order (the UI's diagnostics view). */
+	candidates: Schema.Array(Schema.String),
+	/** The resolved export file, or null if the exporter hasn't written one yet. */
+	file: Schema.NullOr(Schema.String),
+	/** mtime (epoch ms) of the export file, or null. */
+	mtime: Schema.NullOr(Schema.Number),
+	/** True when the file came from `<config_dir>/ingest/playnite` (the reliable lane). */
+	viaIngest: Schema.Boolean,
+});
+export type Location = typeof Location.Type;
+
+/** A game the compute rejected, with a human reason (Library page, CLI). */
+export const SkippedGame = Schema.Struct({
+	id: Schema.String,
+	title: Schema.String,
+	reason: Schema.String,
+});
+export type SkippedGame = typeof SkippedGame.Type;
+
+/** A summary of one desired-state compute (Overview + Library pages). */
+export const SyncReport = Schema.Struct({
+	/** ISO timestamp the exporter stamped on the source export. */
+	generatedAt: Schema.String,
+	/** Schema version of the export that produced this report. */
+	schemaVersion: Schema.Number,
+	/** Games in the export before filtering. */
+	considered: Schema.Number,
+	/** Entries in the reconcile payload. */
+	included: Schema.Number,
+	skipped: Schema.Array(SkippedGame),
+	/** Dropped by an explicit per-game override (the Library page's toggle). */
+	excluded: Schema.Array(
+		Schema.Struct({ id: Schema.String, title: Schema.String }),
+	),
+	warnings: Schema.Array(Schema.String),
+	/** Included entries per Playnite source ("Steam", "GOG", "(none)", …). */
+	perSource: Schema.Record(Schema.String, Schema.Number),
+});
+export type SyncReport = typeof SyncReport.Type;
+
+export const LastSync = Schema.Struct({
+	fingerprint: Schema.String,
+	count: Schema.Number,
+	at: Schema.Number,
+});
+export type LastSync = typeof LastSync.Type;
+
+/** The engine status the Overview page renders and the SSE feed streams. */
+export const EngineStatus = Schema.Struct({
+	platform: Schema.String,
+	location: Location,
+	/** Last read/decode error (missing export, corruption, too-new schema), else null. */
+	exportError: Schema.NullOr(Schema.String),
+	/** Playnite's own version + mode, as stamped on the last readable export. */
+	playnite: Schema.NullOr(
+		Schema.Struct({
+			version: Schema.NullOr(Schema.String),
+			mode: Schema.NullOr(Schema.String),
+		}),
+	),
+	artMode: Schema.String,
+	syncing: Schema.Boolean,
+	lastSync: Schema.NullOr(LastSync),
+	lastReport: Schema.NullOr(SyncReport),
+	paths: Schema.Struct({
+		dir: Schema.String,
+		config: Schema.String,
+		cache: Schema.String,
+		ingest: Schema.String,
+	}),
+});
+export type EngineStatus = typeof EngineStatus.Type;