fix: don't stream when the append IPC is unavailable

Codex re-review: if openRecordingStream exists but appendRecordingChunk
does not (renderer/main version skew), the recorder would open the stream
and switch to streaming mode, but every append silently no-ops and the
save ends up empty. Require both IPC methods before streaming; otherwise
fall back to in-memory buffering. Adds a regression test.

Verified: tsc --noEmit clean; biome clean; vitest 183/183.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/hooks/recorderHandle.test.ts

@@ -205,6 +205,26 @@ describe("createRecorderHandle", () => {
 		expect(blob.size).toBe(2);
 	});
 
+	it("buffers in memory when appendRecordingChunk is unavailable (version skew)", async () => {
+		const openRecordingStream = vi.fn(async () => ({ success: true }));
+		// appendRecordingChunk intentionally omitted to simulate renderer/main skew.
+		stubElectronAPI({ openRecordingStream });
+
+		const handle = createRecorderHandle({} as MediaStream, { mimeType: "video/webm" }, "rec.webm");
+		const fake = driver(handle);
+
+		fake.emit(new Blob(["a"]));
+		await tick();
+		fake.emit(new Blob(["b"]));
+		fake.stop();
+
+		const blob = await handle.recordedBlobPromise;
+		// Never even attempts to open the stream when it can't append to it.
+		expect(openRecordingStream).not.toHaveBeenCalled();
+		expect(handle.isStreaming()).toBe(false);
+		expect(blob.size).toBe(2);
+	});
+
 	it("discard closes the disk stream for a streamed recording", async () => {
 		const closeRecordingStream = vi.fn(async () => ({ success: true }));
 		stubElectronAPI({

src/hooks/recorderHandle.ts

@@ -76,8 +76,14 @@ export function createRecorderHandle(
 		});
 	};
 
+	// Require BOTH stream IPC methods before attempting to stream. If only
+	// openRecordingStream exists (renderer/main version skew), streaming would
+	// open but every append would silently no-op, saving an empty file — so in
+	// that case fall through to in-memory buffering instead.
 	const openPromise: Promise<{ success: boolean; error?: string }> =
-		fileName && api?.openRecordingStream
+		fileName !== undefined &&
+		typeof api?.openRecordingStream === "function" &&
+		typeof api?.appendRecordingChunk === "function"
 			? api.openRecordingStream(fileName)
 			: Promise.resolve({ success: false });