Handle phased animation retargeting

docs/window-animations-testing.md

@@ -288,8 +288,27 @@ Hard failure:
 
 ## 9. Mixed-Action Phases
 
-Look for layouts where one window can move on one axis while another window
-scales on a different axis in the same proven phase.
+This case is easiest to prove with the planner tests because Wry currently has
+few user commands that create a same-batch move for one tiled window and an
+independent resize for another. The canonical geometry is:
+
+```text
+start:  A = (0,0)-(80,80)      B = (200,0)-(280,80)
+target: A = (40,0)-(120,80)    B = (200,0)-(280,120)
+```
+
+`A` moves horizontally while `B` scales vertically. The windows are far enough
+apart that the mixed phase is provably non-overlapping.
+
+To exercise the current proof directly, run:
+
+```sh
+cargo test animation::multiphase::tests::mixed_single_phase_accepts_move_and_scale_when_proven
+```
+
+For visual/manual testing, use any command sequence that can produce the same
+shape in one layout batch: one window changes only x-position, and a separate,
+non-overlapping window changes only height.
 
 Expected:
 
@@ -298,8 +317,8 @@ Expected:
 - no individual window moves diagonally
 - no overlap occurs at any point during the phase
 
-This is easier to confirm with debug fallback logs plus visual inspection. A
-fallback here is acceptable if the planner cannot prove the sequence.
+A fallback here is acceptable if no normal user command can create this geometry;
+the planner test above is the authority for the mixed-action rule.
 
 ## 10. Mono Mode