docs(plans): add playful visual feedback milestone

docs/PLAYER_UI.md

@@ -22,9 +22,9 @@ exit silhouettes remain distinct, and Player 2 uses a dashed secondary
 treatment so ownership does not depend on color alone.
 
 The closed and opened arched exits show the existing locked and opened exit
-states. The crystal represents the existing vision artifact. Spikes appear only
-with local blocked-movement feedback and do not add a trap, damage, protocol,
-or server-state feature.
+states. The crystal represents the existing vision artifact. The spike symbol
+is kept as a local catalog asset but is not shown for blocked movement; it does
+not add a trap, damage, protocol, or server-state feature.
 
 ## Input contract
 
@@ -51,6 +51,21 @@ For every projection, the browser translates only the received cells so the
 authoritative `self` cell stays under the centered avatar; this also keeps the
 avatar off a wall when the visible projection reaches a maze boundary.
 
+## Feedback and message rail
+
+The browser stores the direction for each outstanding move request. Only after
+a matching server `blocked` rejection does it shake the already rendered maze
+in the attempted direction for at most 340 ms; it shows no blocked-move text or spike
+notice. A matching `rate_limited` rejection darkens and blurs only the maze for
+at most 520 ms. Each effect has one restartable timer and is cleared on pause,
+result, reset, disconnect, and control reset. Reduced-motion mode uses a static
+maze border cue for blocked movement instead of a shake.
+
+All remaining Russian system messages use one `role=status` live message rail
+above the application top bar. One connection-loss message has highest priority
+and remains until a successful recovery; other messages deduplicate, replace
+lower-priority content, and dismiss after 2.6 seconds.
+
 Commands use the version-one protocol envelope and contain intention data only:
 
 ```json