Paused window can show no picture until the next key press

Confirmed three independent times on main under load (by the #90, #99, and #101 agents; the #101 confirmation had no audio device and all live files reverted, so it is not content- or audio-related): a PAUSED window sometimes draws bare theme background - no picture - until the next key press forces a redraw. This is the true cause of the flaky 'a toast is drawn clear of the controls' harness check (its before-capture grabs the blank window; 87 percent of pixels then differ). Suspects: the paused redraw path only repaints on request, and under load the last presented frame's surface is lost/invalidated without a repaint being requested (surface reconfigure? buffer swap under memory pressure?). Repro-first: the harness reproduces it under load; instrument which event chain leads to the blank (does the compositor send a configure/frame event the app ignores while paused?). Fix must guarantee: a paused window always shows its frame after any redraw-worthy event. Also fold in #91's harness hardening (before-grabs wait for a non-blank picture) once the app defect is fixed so the harness cannot mask it meanwhile.

Start in the paused window redraw path and compositor event handling: trace configure/frame events and why a redraw is not triggered on pause. Reproduce via the existing harness flow that does before-capture checks (the toast-control path) and confirm whether a paused window presents a blank surface after redraw-worthy events. Then update the #91-related harness hardening so before-grab waits for a non-blank frame. Done looks like no regression under load: paused state always shows the last frame and the flaky blank-capture check no longer fires.

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