feat: feature_index — target individual motors on multi-actuator devices

Ported from the Android edition and completed for the Python relays
(the Android repo only implemented the phone side in Kotlin):

- models.py / mcp_tools.py: optional feature_index on every output and
  pattern tool, passed through to the phone relay.
- relay_client.py: routes targeted writes through buttplug-py's
  per-feature API (device.features[i].run_output) and validates the
  index up front so a bad one fails the ack with the valid indices
  listed, instead of dying silently inside a pattern task.
- termux_relay_v3.py: ScalarCmd entries filtered to the requested
  actuator index, same fallback semantics as the Android relay engine.

Lets Claude drive e.g. a Dolce's internal and external motors
independently (feature_index 0 / 1) instead of always both together.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/mcp_tools.py

@@ -190,13 +190,22 @@ _OUTPUT_PARAMS = {
         "description": "Duration in seconds. 0 = stay on until stop command.",
         "default": 0,
     },
+    "feature_index": {
+        "type": "integer",
+        "description": (
+            "Target a specific actuator by index when a device has multiple "
+            "actuators of the same type (e.g. Dolce motor 0 = primary, "
+            "motor 1 = secondary). Omit to drive all matching actuators together."
+        ),
+    },
 }
 
 
 def _make_output_handler(output_type: OutputType):
     """Factory for output command handlers."""
     async def handler(
-        device: str = "all", intensity: float = 0.5, duration: float = 0, **kw
+        device: str = "all", intensity: float = 0.5, duration: float = 0,
+        feature_index: Optional[int] = None, **kw
     ) -> str:
         clamped = max(0.0, min(1.0, float(intensity)))
         cmd = DeviceCommand(
@@ -204,6 +213,7 @@ def _make_output_handler(output_type: OutputType):
             device=device,
             intensity=clamped,
             duration=max(0.0, float(duration)),
+            feature_index=feature_index,
         )
         return await _send(cmd.model_dump(), intensity=clamped)
     return handler
@@ -311,6 +321,13 @@ _PATTERN_PARAMS = {
         "description": "Duration in seconds",
         "default": 10,
     },
+    "feature_index": {
+        "type": "integer",
+        "description": (
+            "Target a specific actuator by index when a device has multiple "
+            "actuators of the same type. Omit to drive all matching actuators."
+        ),
+    },
 }
 
 
@@ -321,6 +338,7 @@ def _make_pattern_handler(pattern_name: str):
         intensity: float = 0.6,
         duration: float = 10,
         hold_seconds: float = 0,
+        feature_index: Optional[int] = None,
         **kw,
     ) -> str:
         clamped = max(0.0, min(1.0, float(intensity)))
@@ -331,6 +349,7 @@ def _make_pattern_handler(pattern_name: str):
             intensity=clamped,
             duration=max(0.0, float(duration)),
             hold_seconds=max(0.0, float(hold_seconds)),
+            feature_index=feature_index,
         )
         return await _send(cmd.model_dump(), intensity=clamped)
     return handler

server/models.py

@@ -45,6 +45,7 @@ class DeviceCommand(BaseModel):
     device: str = "all"
     intensity: float = Field(0.5, ge=0.0, le=1.0)
     duration: float = Field(0.0, ge=0.0)  # 0 = indefinite
+    feature_index: Optional[int] = None  # target a specific actuator by index
 
 
 class PatternCommand(BaseModel):
@@ -56,6 +57,7 @@ class PatternCommand(BaseModel):
     intensity: float = Field(0.6, ge=0.0, le=1.0)
     duration: float = Field(10.0, ge=0.0)
     hold_seconds: float = Field(0.0, ge=0.0)  # escalate only: 0 = hold at peak indefinitely
+    feature_index: Optional[int] = None  # target a specific actuator by index
 
 
 class StopCommand(BaseModel):