feat: voice-over recording into the timeline

MediaRecorder mic capture (defensive mimeType picking, permission/no-mic
toasts) with elapsed display in the timeline toolbar. Stop produces an
audio asset and inserts it at the playhead on an audio track as ONE
BatchCommand undo step, freeze-frame precedent. voice-over action
registered, no default keybinding. 20 tests; smoke-tested in Chromium
with a fake mic end to end.

1 files changed, 41 insertions, 0 deletions

diff --git a/apps/web/src/voiceover/voiceover-store.ts b/apps/web/src/voiceover/voiceover-store.ts
new file mode 100644
index 00000000..44ccae6c
--- /dev/null
+++ b/apps/web/src/voiceover/voiceover-store.ts
@@ -0,0 +1,41 @@
+/**
+ * Voice-over recording UI state.
+ * Transient by nature — a recording never survives a reload, so unlike most
+ * stores here this one is intentionally NOT persisted (same pattern as
+ * editor-store / properties-store).
+ */
+
+import { create } from "zustand";
+import type { MediaTime } from "@/wasm";
+
+export type VoiceOverStatus = "idle" | "recording";
+
+interface VoiceOverStore {
+	status: VoiceOverStatus;
+	startedAtMs: number | null;
+	playheadStartTime: MediaTime | null;
+	startRecording: ({ playheadTime }: { playheadTime: MediaTime }) => void;
+	stopRecording: () => void;
+}
+
+export const useVoiceOverStore = create<VoiceOverStore>()((set) => ({
+	status: "idle",
+	startedAtMs: null,
+	playheadStartTime: null,
+
+	startRecording: ({ playheadTime }) => {
+		set({
+			status: "recording",
+			startedAtMs: Date.now(),
+			playheadStartTime: playheadTime,
+		});
+	},
+
+	stopRecording: () => {
+		set({
+			status: "idle",
+			startedAtMs: null,
+			playheadStartTime: null,
+		});
+	},
+}));