Add float tile transition animations

docs/window-animations-plan.md

@@ -82,8 +82,8 @@ Implementation shape:
 Initial scope:
 
 - Tiled reflow animation.
-- Floating command-driven moves, tile-to-float, and float-to-tile are deferred
-  until after tiled reflow and spawn-in are validated.
+- Floating command-driven moves are deferred until after tiled reflow, spawn-in,
+  and float/tile transitions are validated.
 - Cross-output and cross-scale movements snap for now.
 - Linear mode may overlap windows during swaps. That is expected for the classic
   interpolation mode; no-overlap is Phase 3.
@@ -100,6 +100,8 @@ Tests:
 - unchanged in-flight windows keep their original timeline
 - drag-driven floating movement bypasses animation
 - damage includes old, current, and final rects
+- command-driven tile-to-float and float-to-tile transitions use linear motion
+- pointer/header double-click unfloat bypasses the command-animation gate
 
 ## Phase 2: Retained Texture Freezing
 
@@ -110,6 +112,8 @@ Initial retained-record implementation status:
 - Tiled animation can retain GPU/dmabuf-backed XDG and Xwayland surface trees.
 - Spawn-in animation can retain GPU/dmabuf-backed XDG and Xwayland surface trees
   for both tiled windows and floating child contents.
+- Tile-to-float and float-to-tile transitions retain GPU/dmabuf-backed child
+  contents while the presentation geometry changes.
 - Retained records hold both `GfxTexture` and `SurfaceBuffer` references so the
   existing buffer release/sync path remains authoritative.
 - Single-pixel buffers can be retained as color records.