Render a smooth cursor, click ripples, zoom on click and follow cursor from the event log

Problem

The recorder deliberately excludes the system cursor. Its clean master shows clicks without a pointer, and a full-page view can be hard to follow. GH-5 now supplies the fitted master and events on the final delivery timeline; GH-7 adds visual emphasis without changing that timeline.

Change

• Automatically polish the MP4 produced by record, using the existing FFmpeg installation. Preserve the clean retimed master, its calibration offset, original speech clips and normalized voice bus (story decisions 012–013; ticket decision 005).
• Draw one white arrow with a dark outline following the logged eased paths. Keep its apparent size constant during zoom. Draw an expanding blue ring at every click, fading over 400 ms (decision 004).
• Clicks trigger a 650 ms eased zoom-in, capped at 4/3 (about 1.33×). Keep zoom until 2000 ms after the most recent click or typing finishes, then ease out over 800 ms. Activity during the zoom extends it; hover and scrolling alone do not trigger zoom (decisions 001–002 and 006).
• Follow the cursor smoothly while zoomed. Add optional CSS target bounds to click and typing events in the compatible version 1 event log. Keep the crop inside the source frame and reduce zoom as needed to show the visible target with padding. Existing logs without bounds use click-point framing, without a whole-element visibility guarantee (decision 003).
• Use the shipped 1440p master for default 1080p delivery. This corrects the earlier 4K wording, superseded by Replay a demo script on a virtual display and write a silent MP4 with step timings #2 decision 005. Optional 4K capture remains in its existing story follow-up.
• Preserve delivery frame count/FPS, speech placement, transcript and caption times. Use final retimed events once, without applying Hold each step for its voice clip, mux the audio, and check sync and reproducibility #5 holds a second time.

Out of scope

Sound effects (GH-8), optional 4K/GPU capture, OS-specific cursor styles, new CLI commands or script controls, intro/outro cards, burned-in captions, and the existing odd-viewport recorder follow-up. No follow-ups are taken up.

Done when

• The sample demo shows the pointer following moves and a ripple beginning at each click's time within one delivery frame.
• Zoom follows the agreed activity timing, stays at or below 4/3, and keeps the visible target bounds framed; oversized or partly off-screen targets are limited by what the clean master actually captured.
• Zoom stays inside the source and does not upscale beyond the available source resolution. Cursor size stays constant at delivery scale.
• Repeated renders of identical master/events/settings produce identical decoded video frames on the same image. Independent browser recordings retain the story's existing ±150 ms comparison contract, rather than requiring identical MP4 bytes.
• Frame count, audio duration/placement, source WAV hashes, transcript/caption times, silent output, and clean-master behavior remain covered by automated checks.
• Unit, media and full recording checks pass; a concrete polished narrated demo is visually reviewed, and render time/memory are recorded.