Add shared piano recording/playback and mono key fallback

docs/controls.md

@@ -81,6 +81,8 @@ Applies to effect select, user/item list modes, item selection, item property li
 - `W E T Y U O P ]`: Play sharps
 - Multiple keys can be held/played at once
 - `-` / `=`: Shift octave down/up
+- `,`: Start/stop recording on this piano (max 30s)
+- `.`: Play back saved recording on this piano
 - `Escape`: Exit piano mode
 
 ## Help Viewer Mode

docs/item-schema.md

@@ -183,6 +183,8 @@
 - `release`: integer, range `0-100`, default `35`.
 - `brightness`: integer, range `0-100`, default `55`.
 - `emitRange`: integer, range `5-20`, default `15`.
+- `recording`: server-managed array of note events (`t`, `keyId`, `midi`, `on`) captured from piano mode recording.
+- `recordingLengthMs`: server-managed recording duration in milliseconds (`0..30000`).
 
 ## Packet Shapes
 

docs/item-types.md

@@ -173,6 +173,8 @@ This is behavior-focused documentation for item types and their defaults.
 
 ### Use
 - Announces that the user begins playing the piano (client enters piano key mode).
+- Piano mode controls include `,` to start/stop recording (max 30s) and `.` to play saved recording.
+- Recordings are stored on the item (server-authoritative), so nearby users hear playback.
 
 ### Validation
 - `instrument`: `piano | electric_piano | guitar | organ | bass | violin | synth_lead | brass | nintendo | drum_kit`

docs/protocol-notes.md

@@ -16,6 +16,7 @@ This is a behavior guide for packet semantics beyond raw schemas.
 - `ping`: latency measurement.
 - `item_add`, `item_pickup`, `item_drop`, `item_delete`, `item_use`, `item_update`: item actions.
 - `item_piano_note`: realtime piano note on/off for active piano use mode.
+- `item_piano_recording`: piano record/playback control (`toggle_record`, `playback`).
 
 ## Server -> Client