fix(relay): clear the demand-expiry timeout on a fence, not only in stop()

Why the existing lifecycle test missed this: it stubs
`demandLedger: { nextPendingExpiry: () => null }`, so the second timer this class
owns is never armed and the fence is only ever asserted against the liveness
interval. Change that one stub to a future expiry and the test fails.

`fenceAndCloseNow` cleared `livenessTimer` and left `demandExpiryTimer` armed.
`stop()` cleared both — but `stop()` has no production caller, while all three
fence sites (quit, sign-out, SIGNED_OUT) go through the path that cleared only one.

The consequence is the sharp part. The orphaned timeout fires `refreshDemand`,
which reconciles *and* re-installs the liveness interval the fence just tore down.
A fence during an outstanding pairing invite therefore undid itself minutes later
— the post-fence resurrection the comment two lines above forbids in so many words.

Both teardown paths now share one `disarmTimers()`. That also resolves the
`max-lines` pressure the extra clause created: the two teardown blocks were byte
identical, so deduplicating them is the right fix rather than a `max-lines`
disable, which this repo forbids and which the next person under that cap will be
tempted by.

The new test asserts `vi.getTimerCount() === 0` after the fence rather than
inferring from an absence of errors, and pins that a fence is not a stop — the
next auth mutation still re-arms both timers.

Pre-existing, not introduced by this stack; verified identical at the base SHA.
Mutation-tested: removing the `demandExpiryTimer` clause from `disarmTimers`
fails the new test at the timer-count assertion.

Also carries a note at `waitForLiveBrokerResult`: the `pending !== latestReconcile`
arm re-enters the loop without re-checking the deadline, so under continuous
reconcile churn the documented 20s budget is not strictly enforced and the
caller's transient demand ref is held past it. Not a hang — every iteration awaits
a settling promise — so it is bounded by how long churn lasts.

src/main/runtime/relay/desktop-relay-service.test.ts

@@ -193,3 +193,48 @@ describe('local-only mobile pairing', () => {
     ).rejects.toThrow('relay_disabled_for_device')
   })
 })
+
+describe('fence clears the pending demand-expiry timeout', () => {
+  afterEach(() => vi.useRealTimers())
+
+  // The lifecycle test above stubs `nextPendingExpiry` to null, so it never arms the second timer
+  // this class owns. With a pairing invite outstanding the fence left that timeout armed, and
+  // `stop()` — the only method that cleared it — has no production caller. The orphaned timeout
+  // then ran `refreshDemand`, which reconciles AND re-installs the liveness interval the fence had
+  // just torn down: the post-fence resurrection the fence comment forbids.
+  it('leaves no armed timer and cannot reconcile after a fence', () => {
+    vi.useFakeTimers()
+    const coordinator = {
+      reconcile: vi.fn(),
+      ensureLive: vi.fn(),
+      fenceAndCloseNow: vi.fn(),
+      stop: vi.fn()
+    }
+    const service = Object.create(DesktopRelayService.prototype) as DesktopRelayService
+    Object.assign(service, {
+      coordinator,
+      // A pending invite: the QR is minted and its server-side expiry is still in the future.
+      demandLedger: { nextPendingExpiry: () => Date.now() + 30_000 },
+      stopped: false,
+      livenessTimer: null,
+      demandExpiryTimer: null
+    })
+
+    service.start()
+    expect(coordinator.reconcile).toHaveBeenCalledTimes(1)
+    expect(vi.getTimerCount()).toBe(2)
+
+    service.fenceAndCloseNow()
+    expect(vi.getTimerCount()).toBe(0)
+
+    vi.advanceTimersByTime(30 * 60_000)
+    expect(coordinator.reconcile).toHaveBeenCalledTimes(1)
+    expect(coordinator.ensureLive).not.toHaveBeenCalled()
+
+    // A fence is not a stop: the next auth mutation still re-arms both timers.
+    service.authMutated()
+    expect(coordinator.reconcile).toHaveBeenCalledTimes(2)
+    expect(vi.getTimerCount()).toBe(2)
+    service.stop()
+  })
+})

src/main/runtime/relay/desktop-relay-service.ts

@@ -111,14 +111,24 @@ export class DesktopRelayService {
     this.refreshDemand()
   }
 
-  fenceAndCloseNow(hostCloseReason?: RelayHostCloseReason): void {
-    // Why: a fence must be hard — a surviving liveness tick could catch the
-    // window between the pre-sign-out fence and the profile wipe and briefly
-    // resurrect a broker. The next auth mutation re-arms via refreshDemand.
+  /** Disarms both timers this class owns. Every teardown needs both: the expiry timeout fires
+   *  `refreshDemand`, which reconciles and re-installs the liveness interval. */
+  private disarmTimers(): void {
+    if (this.demandExpiryTimer) {
+      clearTimeout(this.demandExpiryTimer)
+      this.demandExpiryTimer = null
+    }
     if (this.livenessTimer) {
       clearInterval(this.livenessTimer)
       this.livenessTimer = null
     }
+  }
+
+  fenceAndCloseNow(hostCloseReason?: RelayHostCloseReason): void {
+    // Why: a fence must be hard — a surviving tick could catch the window between
+    // the pre-sign-out fence and the profile wipe and briefly resurrect a broker.
+    // The next auth mutation re-arms via refreshDemand.
+    this.disarmTimers()
     this.coordinator.fenceAndCloseNow(hostCloseReason)
   }
 
@@ -222,14 +232,7 @@ export class DesktopRelayService {
 
   stop(): void {
     this.stopped = true
-    if (this.demandExpiryTimer) {
-      clearTimeout(this.demandExpiryTimer)
-      this.demandExpiryTimer = null
-    }
-    if (this.livenessTimer) {
-      clearInterval(this.livenessTimer)
-      this.livenessTimer = null
-    }
+    this.disarmTimers()
     this.coordinator.stop()
   }