refactor: workspace restructure — contract package + pure domain ported, tests green

- bun workspaces: contract/ (Schemas = source of truth: config raw↔resolved,
  domain DTOs, HttpApi contract, API errors) + plugin/ + ui/
- pure domain moved src/{engine,art}→plugin/src/{domain,art}, types now
  imported from @rom-manager/contract and @punktfunk/plugin-kit/wire (the
  hand-copied wire.ts dies), loggers injected instead of module-global
- ui.* and devEntry dropped from the config shape (standalone server is
  gone; stale keys tolerated on decode, dropped by the next save)
- all 48 domain tests ported and green BEFORE any Effect wiring

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

contract/src/config.ts

@@ -0,0 +1,105 @@
+// The config model. ONE schema: the Encoded side IS the authored file shape (RawConfig),
+// the Type side is the fully-resolved shape the engine consumes (Config). Defaults live
+// ONLY here (`withDecodingDefaultKey` + encodingStrategy "omit") — the kit's ConfigService
+// persists the raw shape verbatim, so a UI save never bakes defaults into the file.
+//
+// Dropped vs 0.2.x: `ui.*` (the standalone password server is gone — console surface +
+// CLI only) and `devEntry` (dev flag out of the prod shape; use `preview` instead).
+// Stale keys in existing files are tolerated on decode and dropped by the next save.
+import { Effect, Schema } from "effect";
+import { EmulatorDef, Platform } from "./domain.js";
+
+const withDefault = <S extends Schema.Top>(
+	schema: S,
+	value: S["Encoded"],
+) =>
+	schema.pipe(
+		Schema.withDecodingDefaultKey(Effect.succeed(value), {
+			encodingStrategy: "omit",
+		}),
+	);
+
+/** A ROM root: a directory paired with the platform its files belong to (design §5). */
+export const RomRoot = Schema.Struct({
+	dir: Schema.String,
+	platform: Schema.String,
+	excludes: Schema.optionalKey(Schema.Array(Schema.String)),
+});
+export type RomRoot = typeof RomRoot.Type;
+
+/** A per-platform launch override — replaces the platform's built-in default. */
+export const PlatformLaunch = Schema.Struct({
+	emulator: Schema.String,
+	core: Schema.optionalKey(Schema.String),
+	extraArgs: Schema.optionalKey(Schema.String),
+});
+export type PlatformLaunch = typeof PlatformLaunch.Type;
+
+/** A per-game override, keyed by `external_id` (`snes/Chrono Trigger (USA).sfc`). */
+export const GameOverride = Schema.Struct({
+	exclude: Schema.optionalKey(Schema.Boolean),
+	emulator: Schema.optionalKey(Schema.String),
+	core: Schema.optionalKey(Schema.String),
+	extraArgs: Schema.optionalKey(Schema.String),
+	title: Schema.optionalKey(Schema.String),
+	art: Schema.optionalKey(Schema.String),
+});
+export type GameOverride = typeof GameOverride.Type;
+
+export const ArtProviderChoice = Schema.Literals([
+	"auto",
+	"steamgriddb",
+	"libretro",
+]);
+export type ArtProviderChoice = typeof ArtProviderChoice.Type;
+
+export const SyncOptions = Schema.Struct({
+	/** Interval poll in minutes (watchers are unreliable on SMB/NFS — poll is primary). */
+	pollMinutes: withDefault(Schema.Number, 15),
+	watch: withDefault(Schema.Boolean, true),
+	debounceMs: withDefault(Schema.Number, 2000),
+	/** Platform ids to region-dedupe ("one entry per title", design §5). */
+	dedupeRegions: withDefault(Schema.Array(Schema.String), []),
+	regionPriority: withDefault(Schema.Array(Schema.String), [
+		"USA",
+		"World",
+		"Europe",
+		"Japan",
+	]),
+	warnEntries: withDefault(Schema.Number, 2000),
+	maxEntries: withDefault(Schema.Number, 5000),
+	closeOnEnd: withDefault(Schema.Boolean, false),
+});
+export type SyncOptions = typeof SyncOptions.Type;
+
+export const ArtOptions = Schema.Struct({
+	enabled: withDefault(Schema.Boolean, true),
+	provider: withDefault(ArtProviderChoice, "auto"),
+	steamGridDbKey: Schema.optionalKey(Schema.String),
+});
+export type ArtOptions = typeof ArtOptions.Type;
+
+export const RomConfigSchema = Schema.Struct({
+	roots: withDefault(Schema.Array(RomRoot), []),
+	platformLaunch: withDefault(Schema.Record(Schema.String, PlatformLaunch), {}),
+	gameOverrides: withDefault(Schema.Record(Schema.String, GameOverride), {}),
+	/** Operator-added / overriding platform defs (merged over built-ins by id). */
+	platforms: Schema.optionalKey(Schema.Array(Platform)),
+	/** Operator-added / overriding emulator defs (merged over built-ins by id). */
+	emulators: Schema.optionalKey(Schema.Array(EmulatorDef)),
+	sync: withDefault(SyncOptions, {}),
+	art: withDefault(ArtOptions, {}),
+});
+
+/** The fully-resolved config the engine consumes. */
+export type Config = typeof RomConfigSchema.Type;
+/** The on-disk config as authored (all optional). */
+export type RawConfig = typeof RomConfigSchema.Encoded;
+
+/**
+ * Resolve an authored raw config to the total shape (defaults filled). Throws on an
+ * invalid shape — the sync path for tests and the UI; the server side uses the kit's
+ * ConfigService (Effect + typed errors) instead.
+ */
+export const resolveConfig = (raw: unknown): Config =>
+	Schema.decodeUnknownSync(RomConfigSchema)(raw);