Replace Pid.scale()'s mutable gain factor with a stateless process() arg

Pid.scale(k) set self.k as persistent state, mutated from outside the
class and never reset in reset(), so a stale scale factor could survive
a state-transition reset. Replace it with a plain scale=1.0 argument on
Pid.process(), and have temp_controller.py/temp_controller_smith.py
compute the heat-rate-overshoot compensation factor themselves and pass
it through process_pid() each tick instead of mutating pid_hold's state.

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

components/pid/pid.py

@@ -5,8 +5,6 @@ class Pid:
         self.dt = dt
         self.params = None
 
-        self.k = 1.0
-
         # Integrator
         self.yi = 0
 
@@ -21,9 +19,6 @@ class Pid:
         # Output
         self.y = 0
 
-    def scale(self, k):
-        self.k = k
-
     def set_params(self, params):
         self.params = params
 
@@ -32,12 +27,12 @@ class Pid:
         self.d = 0
         self.awu = 0
 
-    def process(self, err, d):
+    def process(self, err, d, scale=1.0):
         dt = self.dt
-        kp = self.params['kp'] * self.k
-        ki = self.params['ki'] * self.k
-        kd = self.params['kd'] * self.k
-        kt = self.params['kt'] * self.k
+        kp = self.params['kp'] * scale
+        ki = self.params['ki'] * scale
+        kd = self.params['kd'] * scale
+        kt = self.params['kt'] * scale
 
         self.yi = self.yi + ki*dt * err + kt*dt * self.awu
         yd = kd/dt*(d - self.d)