feat(sync): headless --sync-cli mode so sync only needs the app installed

The Electron app now answers launcher-style sync argv (--sync-cli sync
[host|--snapshot|--merge] ... plus --help/--version) at entry, before any
window or display initialization, backed by a libsql binding of the shared
stats-sync engine. Works over SSH with no display server, so a remote
machine no longer needs the bun launcher. The launcher accepts --sync-cli
as a no-op so both invocation shapes stay equivalent.

launcher/test-support/immersion-db-fixture.d.ts

@@ -0,0 +1,28 @@
+export declare function createImmersionDbFixture(dbPath: string): void;
+export interface FixtureSessionInput {
+    uuid: string;
+    videoKey: string;
+    animeTitleKey?: string | null;
+    animeEpisodesTotal?: number | null;
+    startedAtMs: number;
+    endedAtMs?: number | null;
+    activeWatchedMs?: number;
+    cardsMined?: number;
+    linesSeen?: number;
+    tokensSeen?: number;
+    watched?: boolean;
+    words?: Array<{
+        headword: string;
+        word: string;
+        reading: string;
+        count: number;
+    }>;
+    applyLifetime?: boolean;
+}
+/**
+ * Insert a session (with video/anime/subtitle-line/occurrence rows) the way
+ * the app would have recorded it, optionally crediting lifetime aggregates
+ * the way applySessionLifetimeSummary does for locally-recorded sessions.
+ */
+export declare function insertFixtureSession(dbPath: string, input: FixtureSessionInput): void;
+//# sourceMappingURL=immersion-db-fixture.d.ts.map