feat: load air-piano and hook hand modulation

Wire finger_piano.scd into both data-only boot paths so
OSCdef /pose/finger and ~fp* API are available at runtime.
Call ~fpModTick on every /pose/hands frame (~30 Hz) for
continuous air-piano modulation. Document FINGER_PIANO env
vars in CLAUDE.md.

CLAUDE.md

@@ -68,6 +68,9 @@ Toujours répondre en français à l'utilisateur. Code, commentaires de code, co
 | `ICP_LIDAR_HOST` | _(unset)_ | iPhone ARBodyTracker IP when `ICP_FUSION=1` |
 | `ICP_LIDAR_PORT` | `5500` | iPhone ARMesh TCP port |
 | `ICP_LIDAR_EXTRINSIC` | `~/.config/av-live/lidar_extrinsic.json` | extrinsic JSON path |
+| `FINGER_PIANO` | `0` | `1` enables air-piano finger strike emission from data_only_viz |
+| `FINGER_STRIKE_VEL` | `0.02` | downward relative-velocity threshold for a strike (normalized image units/frame) |
+| `FINGER_STRIKE_REFRACTORY_MS` | `120` | min ms between strikes per finger |
 
 ## Conventions globales
 

sound_algo/boot.data-only.scd

@@ -38,6 +38,7 @@ Routine({
 
     "[boot.data-only] loading data_feeds OSCdef...".postln;
     (~base ++ "control/data_feeds.scd").load;
+    (~base ++ "control/finger_piano.scd").load;
     1.0.wait;
 
     "[boot.data-only] loading web_bridge OSCdef + sync push...".postln;

sound_algo/control/data_feeds.scd

@@ -509,6 +509,7 @@ OSCdef(\poseHands, { |msg|
     ~handFeat[\ropen]  = msg[8];
     ~handFeat[\rspeed] = msg[9];
     ~handFeat[\dist]   = msg[10];
+    ~fpModTick !? { ~fpModTick.value };   // air-piano modulation continue
 }, '/pose/hands');
 
 // Body wrists (skeleton, tracked even when hands are occluded/too small).

sound_algo/data_only/boot.scd

@@ -149,6 +149,7 @@ Routine({
 
     // -- 5) OSCdef des flux data_feeds -----
     (~repoRoot ++ "control/data_feeds.scd").load;
+    (~repoRoot ++ "control/finger_piano.scd").load;
     0.5.wait;
 
     // -- 6) Bibliotheque de scenes -----