Flaky Dex Web test: WorkQueueSearch counts an extra search after a checkbox change #1600

Problem

web/app/work-queue/WorkQueueSearch.test.tsx > "Work Queue search" > "searches several Flow types in one request and offers all their Steps" fails intermittently in CI on pull requests that do not touch Dex Web:

AssertionError: expected 1 to be +0 // Object.is equality
 ❯ app/work-queue/WorkQueueSearch.test.tsx:193:29
    193| expect(searches.length).toBe(searchesBefore);

The test clicks a checkbox in the advanced panel (line 192) and then expects no new search before submit(); one extra search request was recorded.

Observed on 2026-11-11:

• PR Docs: describe ID reuse policies and start request IDs as the server implements them #1584 (proto comments and docs only), job "Build and local-stack integration", run 42955770315; passed on rerun.
• PR server-zd and SDKs: acknowledge SubFlow starts on completion; reject SubFlows from dashed Step types #1574 (server-zd SubFlow fix), Go SDK CI job "Integration coverage (zd, pull)", run 42962203519, step that builds the embedded Web assets.

Hypothesis (unverified): the checkbox change triggers a debounced or effect-driven search whose timing races with the assertion, so the count depends on scheduling.

Where to look

• web/app/work-queue/WorkQueueSearch.test.tsx around lines 180-200.
• The Work Queue search component's effects and debounce that issue search requests when filter controls change.

Acceptance

• Find the cause and fix the test or the component so the assertion is deterministic (fake timers or awaiting the settled state; or no search on that checkbox change if that is the intended behavior).
• The test passes 50 consecutive runs locally (vitest run --repeat or a loop).