feat(SAC_LSTM_Bot): action mapping module (#43)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SAC_LSTM_Bot/src/SAC_LSTM_Bot/actions.nim

@@ -0,0 +1,36 @@
+## actions.nim — map raw network output (4 tanh values) to bot intent fields.
+##
+## Note on acceleration vs targetSpeed:
+##   TankRoyale uses setTargetSpeed(), not setAcceleration().
+##   The mapped `acceleration` field is a delta; callers must compute:
+##     newTargetSpeed = clamp(currentSpeed + acceleration, -8.0, 8.0)
+##   and call setTargetSpeed(newTargetSpeed).
+
+import arraymancer
+
+const ACTION_DIM* = 4
+
+type
+  MappedActions* = object
+    turnRate*:    float  ## degrees/tick, speed-aware; [-10, 10] at speed 0
+    acceleration*: float ## delta speed in [-2, +1]; caller adds to currentSpeed
+    gunTurnRate*: float  ## degrees/tick in [-20, 20]
+    firePower*:   float  ## 0 = don't fire; (0.1, 3.0] = fire with this power
+
+proc mapActions*(networkOutput: Tensor[float32],
+                 currentSpeed: float,
+                 gunHeat: float): MappedActions =
+  ## networkOutput: [4] tensor of tanh values in [-1, 1].
+  let a0 = networkOutput[0].float
+  let a1 = networkOutput[1].float
+  let a2 = networkOutput[2].float
+  let a3 = networkOutput[3].float
+
+  result.turnRate    = a0 * (10.0 - 0.75 * abs(currentSpeed))
+  # asymmetric accel: [-1,1] -> [-2, +1] via (value * 1.5 - 0.5)
+  result.acceleration = a1 * 1.5 - 0.5
+  result.gunTurnRate = a2 * 20.0
+  if a3 > 0.0 and gunHeat <= 0.0:
+    result.firePower = a3 * 2.9 + 0.1
+  else:
+    result.firePower = 0.0