test(pause-api): harden "reject in-flight" test with durability assertion

Strengthen test to prove the job's paused state remains unmodified when
pause/unpause is rejected for a downloading job. Tests now seeds paused=true,
attempts paused=false, verifies 400, and fetches from DB to assert paused is
still true — catching regressions that would mutate before the guard check.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/api/requests/[id]/pause/route.test.ts

@@ -35,9 +35,11 @@ describe("per-item pause API", () => {
   });
 
   it("rejects pausing an in-flight job", async () => {
-    const created = await seed({ state: "downloading" });
-    const res = await POST(req(created.id, true), { params: Promise.resolve({ id: created.id }) });
+    const created = await seed({ state: "downloading", paused: true });
+    const res = await POST(req(created.id, false), { params: Promise.resolve({ id: created.id }) });
     expect(res.status).toBe(400);
+    const job = await prisma.job.findUnique({ where: { id: created.job!.id } });
+    expect(job?.paused).toBe(true);
   });
 
   it("404s for a missing request", async () => {