feat: auto-regenerate preview on settings change

[Copilot]

Previously, changing any padding setting required a manual "Process Images" click to see the result. A stale "Settings changed — re-process to apply" warning was the only feedback.

Changes

src/App.tsx

• Replaces the settingsChangedSinceProcess state + amber warning with a debounced auto-process on every settings change
• Two new refs drive this safely:
  • handleProcessRef — updated after every render via a no-dep useEffect, so the debounce timer always invokes the closure with the freshest photos/settings
  • autoProcessTimerRef — cancels the previous timer on rapid changes (e.g. dragging a slider), firing only 400 ms after the last change

// syncs ref to freshest handleProcess after every render
useEffect(() => { handleProcessRef.current = handleProcess; });

// debounced auto-process; only fires when photos are already loaded
useEffect(() => {
  if (isInitialMountRef.current) { isInitialMountRef.current = false; return; }
  if (photos.length === 0) return;
  clearTimeout(autoProcessTimerRef.current);
  autoProcessTimerRef.current = setTimeout(() => handleProcessRef.current(), 400);
  return () => clearTimeout(autoProcessTimerRef.current);
}, [settings]); // eslint-disable-line react-hooks/exhaustive-deps

• onChange handler simplified — setIsProcessed(false) hides the Download button during the debounce window; it reappears once auto-processing completes
• "Process Images" button retained for the initial manual trigger and as a fallback

src/__tests__/App.test.tsx

• Asserts the removed warning never appears after a settings change
• Asserts Download All as ZIP disappears on settings change then reappears once the debounced auto-process completes

[github-actions]

🎭 Playwright UI Test Results

✅ All UI tests passed

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[esmcelroy]

@copilot Can we ensure linting passes

[Copilot]

@copilot Can we ensure linting passes

Fixed in bff56dc. The 21 pre-existing ESLint errors were spread across 6 files:

• e2e/settings.spec.ts — removed unused createLandscapePng/uploadTestImage imports
• App.test.tsx — replaced as any with as unknown as <T> for the matchMedia and FileReader mocks
• PhotoGrid.test.tsx — removed unused beforeEach import; replaced as any with typed casts for anchor/ClipboardItem/fetch mocks
• heicUtils.test.ts — replaced as any with as unknown as HTMLCanvasElement in the createElement spy
• useDarkMode.test.ts — replaced as any with as unknown as typeof window.matchMedia
• imageUtils.test.ts — removed unused WatermarkPosition import, unused _quality param, unused result variables; fixed no-this-alias by converting the set accessor to an arrow function

npm run lint now exits cleanly with zero errors.

[github-actions]

🎭 Playwright UI Test Results

✅ All UI tests passed

View full report →