Clean up IndexedDB previous-page listener

[issackjohn]

Summary

• Replace the resolver stored on iterationFinishedListener with a per-navigation promise.
• Register a one-shot previous-page-loaded listener before clicking the Previous button, then await that page transition.
• Keep the checked-in dist workload in sync with the source.

Why

The previous implementation kept mutable resolver state on a function object and registered a listener that was never removed. Scoping each listener to one page transition makes the control flow explicit and cleans it up automatically after the event fires.

Validation

• git diff --check

Closes #52.

[Copilot]

Pull request overview

This PR cleans up the IndexedDB TodoMVC benchmark’s “previous page loaded” synchronization by replacing a shared, hidden promiseResolve function property with a per-transition one-shot promise tied to the previous-page-loaded event. This makes page-transition waiting deterministic (listener installed immediately before the click) and ensures the listener is automatically removed after firing.

Changes:

• Replace the persistent previous-page-loaded listener + iterationFinishedListener.promiseResolve state with waitForPreviousPageLoaded() that uses addEventListener(..., { once: true }).
• Register the listener immediately before clicking the previous-page button, then await the resulting promise.
• Apply the same update to both the source and generated dist workload test files.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
experimental/javascript-wc-indexeddb/src/workload-test.mjs	Switches “previous page loaded” waiting logic to a per-iteration one-shot promise to avoid missed events and hidden listener state.
experimental/javascript-wc-indexeddb/dist/src/workload-test.mjs	Keeps generated dist workload test in sync with the updated source behavior.

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