fix(studio): let only user input hold back font list idle work, and retry after a failure

[miguel-heygen]

Stacked on #4794. Retarget to main once that merges.

What

Three follow-ups to the idle font-list processing:

1. Only the user's input holds the work back. The idle gate used the overlay loop's awake window, and that window is also extended by playback frames and by programmatic wakes. During a long playback the picker therefore stayed on the popular fonts. The gate now reads its own last-input time, which comes from pointer, key and wheel events only (INPUT_EVENTS; the loop's wake sources are those plus scroll, resize and visibility). The input listeners attach with the first overlay subscriber, so input that happens before the lists arrive still counts.
2. A failure in the idle step no longer leaves "Loading" forever. The step catches the error, logs it, and clears the request, so the next mount or picker open retries.
3. Input that lands after an idle slice was queued holds that slice back. A test now covers this; the behaviour was already there.

Tests

overlayFrameLoop.test.ts:

• "holds an idle slice when input lands after it was queued";
• "does not hold idle work for playback frames or programmatic wakes".

propertyPanelFont.test.tsx:

• "retries on the next open when processing the lists throws".

All three fail with the two source files at #4794's head. With the re-check at the idle callback removed, the first one fails.