feat: git-like project versioning (v1)

Linear per-project history per notes/project-versioning.md: named
checkpoints (thumbnail via renderer.captureFrame) plus auto-checkpoints
on save (60s throttle, ring of 20, named never rotate). Restore writes a
safety checkpoint first, then swaps the document outside undo/redo.
Media assets referenced by any version are pinned against deletion.
Migration v31-v32 stamps the schema; the version store lives in its own
IDB database with an in-memory fallback for tests. Versions popover in
the editor header for jump/rename/delete. 12 new tests.

1 files changed, 52 insertions, 0 deletions

diff --git a/apps/web/src/versions/media-references.ts b/apps/web/src/versions/media-references.ts
new file mode 100644
index 00000000..86264320
--- /dev/null
+++ b/apps/web/src/versions/media-references.ts
@@ -0,0 +1,52 @@
+import type { SerializedProject } from "@/services/storage/types";
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+	return typeof value === "object" && value !== null && !Array.isArray(value);
+}
+
+function collectFromElements({
+	elements,
+	mediaIds,
+}: {
+	elements: unknown;
+	mediaIds: Set<string>;
+}): void {
+	if (!Array.isArray(elements)) return;
+
+	for (const element of elements) {
+		if (!isRecord(element)) continue;
+		if (typeof element.mediaId === "string" && element.mediaId.length > 0) {
+			mediaIds.add(element.mediaId);
+		}
+	}
+}
+
+/**
+ * Extracts every media asset id referenced by a serialized project's scenes.
+ * Duck-typed (like migrations) so snapshots of any project version scan safely.
+ */
+export function getReferencedMediaIds({
+	project,
+}: {
+	project: SerializedProject;
+}): Set<string> {
+	const mediaIds = new Set<string>();
+
+	for (const scene of project.scenes ?? []) {
+		const tracks: unknown = scene.tracks;
+		if (!isRecord(tracks)) continue;
+
+		if (isRecord(tracks.main)) {
+			collectFromElements({ elements: tracks.main.elements, mediaIds });
+		}
+		for (const list of [tracks.overlay, tracks.audio]) {
+			if (!Array.isArray(list)) continue;
+			for (const track of list) {
+				if (!isRecord(track)) continue;
+				collectFromElements({ elements: track.elements, mediaIds });
+			}
+		}
+	}
+
+	return mediaIds;
+}