Capture the screen slightly before each click; record milestone in CHANGELOG

Real-world recording now saves every click with exact markers; the only
remaining nit was screenshots feeling a touch late. Add a configurable
click-lead (capture.clickLeadMs, default 120ms) that targets the screen
just before the hook timestamp, and tighten the stream sampling cadence to
50ms so a frame near that target always exists. Verified end to end: frames
now land ~120-160ms before the click (was 25-57ms), markers stay at 0.00%
offset, and the 8-click burst still saves all 8.

Also document the milestone in docs/CHANGELOG.md and remove an accidental
paste of Gitea commit-page text from it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/renderer/capture-worker.js

@@ -22,10 +22,11 @@
 /* global StepForgeClickFrames, captureWorkerBridge */
 
 (() => {
-  const FALLBACK_SAMPLE_MS = 100;
-  // Tight cadence means more frames per second; keep enough of them to
-  // bridge any encode/IPC hiccup without hoarding GPU memory.
-  const FALLBACK_FRAME_LIMIT = 8;
+  const FALLBACK_SAMPLE_MS = 50;
+  // Tight cadence means more frames per second; keep enough of them to span
+  // the click-lead window plus any encode/IPC hiccup, without hoarding GPU
+  // memory. 16 frames at the 50ms cadence is ~800ms of history.
+  const FALLBACK_FRAME_LIMIT = 16;
   const FALLBACK_RETENTION_MS = 2000;
 
   const streams = new Map(); // displayId(string) -> stream state