fix(api): harden broadcast and assistant fallback errors

packages/api/src/__tests__/assistant-tools-advanced.test.ts

@@ -1374,6 +1374,51 @@ describe("assistant advanced tools and scoping", () => {
     });
   });
 
+  it("returns a stable demand-requirement-not-found error for batch timeline shifts", async () => {
+    const demandRequirement = {
+      id: "demand_requirement_1",
+      startDate: new Date("2026-03-10"),
+      endDate: new Date("2026-03-14"),
+    };
+    const db = {
+      allocation: {
+        findUnique: vi.fn().mockResolvedValue(null),
+      },
+      demandRequirement: {
+        findUnique: vi.fn().mockResolvedValue(demandRequirement),
+      },
+      assignment: {
+        findUnique: vi.fn().mockResolvedValue(null),
+      },
+      $transaction: vi.fn(async () => {
+        throw new TRPCError({
+          code: "NOT_FOUND",
+          message: "Demand requirement not found",
+        });
+      }),
+    };
+    const ctx = createToolContext(
+      db,
+      [PermissionKey.MANAGE_ALLOCATIONS, PermissionKey.USE_ASSISTANT_ADVANCED_TOOLS],
+      SystemRole.MANAGER,
+    );
+
+    const result = await executeTool(
+      "batch_shift_timeline_allocations",
+      JSON.stringify({
+        allocationIds: ["demand_requirement_missing"],
+        daysDelta: 3,
+        mode: "move",
+      }),
+      ctx,
+    );
+
+    expect(result.action).toBeUndefined();
+    expect(JSON.parse(result.content)).toEqual({
+      error: "Demand requirement not found with the given criteria.",
+    });
+  });
+
   it("returns the chargeability report readmodel through the assistant", async () => {
     const { listAssignmentBookings } = await import("@capakraken/application");
     vi.mocked(listAssignmentBookings).mockResolvedValue([