feat(tests): let managers escalate and directly resolve disputed tests

Request Discussion only ever nudged the peer lead, and the one-time
manager notification when a dispute starts had no real follow-up
action attached to it — a manager could be told a dispute existed but
had no way to actually do anything about it. Adds:

- POST /tests/{id}/escalate-to-manager — either lead can explicitly
  ask managers to step in, distinct from the passive initial notice.
- POST /tests/{id}/manager-resolve-dispute — a manager decides the
  final outcome (validated/rejected) directly, bypassing both leads'
  votes entirely, reusing the same dual-validation event dispatch so
  Jira/notifications behave like any other resolution.

Both leads are notified of the manager's final call, win or lose.

frontend/src/api/tests.ts

@@ -319,6 +319,26 @@ export async function resolveDispute(testId: string, payload: ResolveDisputePayl
   return data;
 }
 
+/** Either lead on a disputed test asks a manager to step in and decide. */
+export async function escalateToManager(testId: string): Promise<{ status: string; message: string }> {
+  const { data } = await client.post(`/tests/${testId}/escalate-to-manager`);
+  return data;
+}
+
+export interface ManagerResolveDisputePayload {
+  outcome: "validated" | "rejected";
+  notes?: string;
+}
+
+/** A manager decides the final outcome of a disputed test directly. */
+export async function managerResolveDispute(
+  testId: string,
+  payload: ManagerResolveDisputePayload,
+): Promise<Test> {
+  const { data } = await client.post<Test>(`/tests/${testId}/manager-resolve-dispute`, payload);
+  return data;
+}
+
 // ── Reopen ─────────────────────────────────────────────────────────
 
 /** Reopen a rejected test — moves back to draft. */