fix(gateway): debug log floods with event-loop-health scheduler lines (#161895)

* fix(gateway): debug log floods with event-loop-health scheduler lines

Since event-loop sampling moved onto the Gateway scheduler as a 20 ms
cadence job, the scheduler's per-run "running <id>" debug line fires about
47 times a second. With logging.level "debug" that line is about 98% of
the file log, so the default rolling log keeps only about 8 hours.

Log repeating cadence runs at trace and keep one-shot runs at debug.
Run failures still log at error.

Closes #161891

* test(hooks): give the Gmail watcher's logger mock a trace method

The Gmail watcher renews through a Gateway scheduler cadence job, whose
per-run line is now logged at trace. The test's subsystem logger mock had
no trace method, so every renewal threw "log.trace is not a function".

src/hooks/gmail-ops.test.ts

@@ -11,7 +11,7 @@ const mocks = vi.hoisted(() => ({
   runCommandWithTimeout: vi.fn(),
   killProcessTree: vi.fn(),
   spawn: vi.fn(),
-  log: { debug: vi.fn(), error: vi.fn(), warn: vi.fn(), info: vi.fn() },
+  log: { debug: vi.fn(), trace: vi.fn(), error: vi.fn(), warn: vi.fn(), info: vi.fn() },
   defaultRuntime: {
     log: vi.fn(),
     error: vi.fn(),

src/infra/gateway-scheduler.test.ts

@@ -7,6 +7,11 @@ import {
   createTestGatewayScheduler,
 } from "../test-utils/gateway-scheduler-clock.js";
 
+const schedulerLog = vi.hoisted(() => ({ debug: vi.fn(), trace: vi.fn(), error: vi.fn() }));
+vi.mock("../logging/subsystem.js", () => ({
+  createSubsystemLogger: () => schedulerLog,
+}));
+
 function fixture() {
   const time = createGatewaySchedulerClock(1_000);
   const scheduler = createTestGatewayScheduler(time.clock);
@@ -331,6 +336,26 @@ describe("Gateway timed work", () => {
     await scheduler.stop();
   });
 
+  it("logs one-shot runs at debug and repeating cadence runs only at trace", async () => {
+    const { time, scheduler } = fixture();
+    schedulerLog.debug.mockClear();
+    schedulerLog.trace.mockClear();
+    const sample = vi.fn();
+    scheduler.schedule({ id: "event-loop-health", delayMs: 20, everyMs: 20, run: sample });
+    scheduler.schedule({ id: "approval", delayMs: 30, run: () => {} });
+    await time.advanceBy(20);
+    await time.advanceBy(20);
+    await time.advanceBy(20);
+    expect(sample).toHaveBeenCalledTimes(3);
+    expect(schedulerLog.debug.mock.calls).toEqual([["running approval"]]);
+    expect(schedulerLog.trace.mock.calls).toEqual([
+      ["running event-loop-health"],
+      ["running event-loop-health"],
+      ["running event-loop-health"],
+    ]);
+    await scheduler.stop();
+  });
+
   it("retains a distant deadline across the host timer delay ceiling", async () => {
     const { time, scheduler } = fixture();
     const run = vi.fn();

src/infra/gateway-scheduler.ts

@@ -274,7 +274,13 @@ export class GatewayScheduler {
   }
 
   private run(job: ScheduledWork): Promise<void> {
-    log.debug(`running ${job.id}`);
+    // Cadence jobs can run every few milliseconds (event-loop sampling runs every 20ms),
+    // so only one-shot runs are worth a debug line.
+    if (job.everyMs === undefined) {
+      log.debug(`running ${job.id}`);
+    } else {
+      log.trace(`running ${job.id}`);
+    }
     const done = createDeferredCore();
     const work = new AsyncWorkScope();
     job.running = done.promise;