fix(client): repair the TypeScript build

`npm run build` runs `tsc -b` first and it has been failing: `api.ts` used
`NamedLock` without importing it, and four lane test fixtures predate
`Lane.active_feature_id` / the widened `LaneRuntime`, so spreading a
`Partial<Lane>` over them no longer satisfied the required fields.

Nothing shipped could be rebuilt while this was red, which is how a client
change reaches a dashboard running in production mode. The fixture fixes are
casts with a note, not type relaxations — the base literals still list every
required field, so the assertion states what they already prove.

client/src/pages/__tests__/Workspace.test.tsx

@@ -24,6 +24,7 @@ type LaneFixture = {
   pipeline_nodes: never[];
   detected_signal: string | null;
   run_id: string | null;
+  active_feature_id?: number | null;
 };
 
 let lanesToReturn: LaneFixture[] = [
@@ -583,7 +584,8 @@ describe("Workspace — proof gallery", () => {
       ],
     });
     // Set active_feature_id and ensure features list is populated
-    lanesToReturn[0].active_feature_id = 1;
+    // (indexed access is `| undefined` under noUncheckedIndexedAccess)
+    lanesToReturn[0]!.active_feature_id = 1;
     vi.mocked(api.lanes.features.list).mockResolvedValue({
       features: [
         {