Add Shift+Enter secondary item action with radio handler

docs/controls.md

@@ -28,6 +28,7 @@ This document is the authoritative keymap for the client.
 - `D`: Pick up/drop item
 - `Shift+D`: Delete item
 - `Enter`: Use item
+- `Shift+Enter`: Secondary item action
 
 ### Audio
 - `P`: Ping server

docs/item-types.md

@@ -38,6 +38,7 @@ This is behavior-focused documentation for item types and their defaults.
 
 ### Use
 - `use` toggles `enabled` on/off and broadcasts chat status.
+- `secondary use` reports now-playing metadata (`Playing <song> from <station>`), or `<title> is off` when disabled.
 
 ### Validation
 - `mediaChannel`: `stereo | mono | left | right`

docs/protocol-notes.md

@@ -20,6 +20,7 @@ This is a behavior guide for packet semantics beyond raw schemas.
 - `chat_message`: player chat.
 - `ping`: latency measurement.
 - `item_add`, `item_pickup`, `item_drop`, `item_delete`, `item_use`, `item_update`: item actions.
+- `item_secondary_use`: trigger type-specific secondary action when implemented.
 - `item_piano_note`: realtime piano note on/off for active piano use mode.
 - `item_piano_recording`: piano record/playback control (`toggle_record`, `playback`, `stop_playback`).