Feature: Reel mode (9:16), zoom-out blur background, per-section PIP scale

[amitayks]

Summary

Three related features for vertical video export and enhanced PIP control:

1. Reel Mode (9:16 Vertical Output)

• New outputMode setting to switch between 16:9 landscape and 9:16 reel
• Per-section reelCropX property to select which horizontal strip of the 16:9 source to crop
• Crop overlay in editor preview with draggable repositioning
• Smooth animated crop transitions between sections (0.3s)
• Crop preset buttons (left/center/right)

2. Zoom-Out with Blur Background (Reel Mode)

• Extended zoom range to 0.5–3.0 in reel mode (was 1.0–3.0)
• When zoom < 1.0, content is scaled down and centered on a darkened background (20% brightness)
• Smooth transitions when zoom crosses the 1.0 boundary

3. Per-Section PIP Scale

• pipScale is now a per-keyframe property (0.15–0.50) instead of a global setting
• Each section can have a different PIP size with smooth animated transitions
• Two-stage ffmpeg scale pipeline to handle variable-size PIP with round corners

4. Per-Mode State Save/Restore

• Toggling between 9:16 (reel) and 16:9 (landscape) previously destroyed per-section settings (zoom, pan, PIP position/scale)
• Now each mode independently remembers its visual state via savedLandscape/savedReel slots on each keyframe
• Switching modes saves current state and restores the target mode's state (or applies defaults on first entry)

5. Reel Crop Fit-Content Bounds

• In reel mode with screenFitMode: 'fit', the source video may be narrower than the canvas, creating black bars
• The crop region now constrains to the actual video content edges instead of the full canvas width
• When zoom-out and fit mode are combined, both constraints stack: contentW * zoom determines the crop range
• Prevents black side bars from appearing in the reel output

Bug Fixes

• resolveOutputSize() now correctly uses sourceHeight parameter
• Camera black fallback uses correct dimensions per output mode
• Overlay filter now includes eval=frame for animated PIP positioning
• snapToNearestCorner() accepts effective canvas dimensions instead of hardcoded globals

Tests

• Comprehensive unit tests for all new domain normalizers, render filter logic, and render service changes

Related Commits

• fd70cab — feat: add reel mode (9:16), zoom-out blur background, and per-section PIP scale
• 06135bc — feat: save/restore per-mode visual state when toggling 9:16/16:9
• 6596bf0 — feat: constrain reel crop to actual content edges in fit mode
• 324dffb — feat: add 9-point PIP snap grid with per-section/per-mode persistence
• f77d245 — fix: reel render crash, zoom-out blur bleed, and per-mode state loss