Use vi.waitFor in app event watcher test

[alfonso-noriega]

WHY are these changes introduced?

Fixes N/A

app-event-watcher.test.ts had a hand-rolled polling loop using setTimeout to wait for async watcher emissions. Using Vitest's built-in wait helper makes the test easier to read and avoids maintaining custom timer logic.

WHAT is this pull request doing?

Replaces the custom new Promise / setTimeout polling loop with vi.waitFor while preserving the same timeout and polling interval semantics. The assertions still wait for both all and ready events before continuing.

How to test your changes?

Validated locally from ~/worktrees/cli-use-vi-waitfor-app-event-watcher:

pnpm install --frozen-lockfile
pnpm --filter @shopify/app vitest src/cli/services/dev/app-events/app-event-watcher.test.ts --run
pnpm --filter @shopify/app lint
NX_SKIP_NX_CACHE=true pnpm --filter @shopify/app type-check
git diff --check

Post-release steps

None.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• This change is not user-facing, so no changeset is required

[alfonso-noriega]

• Use vi.waitFor in app event watcher test #7845 👈 (View in Graphite)
• main

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