pid: option A heat-rate pre-filter (beta IIR before differentiation)

Adds a configurable IIR pre-filter (beta, default 0.05, τ≈19 s at dt=1 s)
applied to theta_ist before the derivative, so stirrer-induced temperature
noise is attenuated before being amplified by differentiation rather than
after.  The shared filter/derivative/post-filter logic is factored into
TempControllerBase._compute_heatrate(); both Normal and Smith subclasses
call it, replacing their duplicated inline rate blocks.

beta is read from TempCtrl.beta in the config (default 0.05 if absent) and
added to config-sim.json.tpl and config-real.json.tpl.

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

components/pid/temp_controller_smith.py

@@ -5,17 +5,8 @@ from components.pid.temp_controller_base import TempControllerBase, States
 class TempController(TempControllerBase):
 	def __init__(self, dt):
 		TempControllerBase.__init__(self, dt)
-		self.dt = dt
-		# None until the first process() tick - rather than hardcoding a
-		# starting point (e.g. 20), which would make that very first
-		# tick's heatrate come out as a bogus spike whenever the real
-		# starting temperature isn't actually 20 (see
-		# components/sud_forecast.py's SudForecastEstimator, which builds
-		# a fresh TempController on every call - unlike the real one,
-		# which only ever goes through this exactly once, it has no
-		# earlier ticks to have already settled past that spike by).
-		self.last_theta_ist = None
-		self.heatrate_ist = 0
+		# last_theta_ist / theta_ist_filtered / beta / dt all live in the base -
+		# see TempControllerBase.__init__ and _compute_heatrate().
 
 		# Fast model: same plant model but with zero transport delay, used
 		# to predict the current temperature without the dead time.
@@ -68,11 +59,7 @@ class TempController(TempControllerBase):
 		# so the dead time drops out of the feedback path.
 		self.theta_ist = self.theta_ist_model + (self.theta_ist_plant - self.theta_ist_model_delay)
 
-		heatrate = 0 if self.last_theta_ist is None else (self.theta_ist - self.last_theta_ist)/self.dt*60
-
-		alpha = 0.1
-		self.heatrate_ist = (1-alpha) * self.heatrate_ist + alpha*heatrate
-		self.last_theta_ist = self.theta_ist
+		self._compute_heatrate(self.theta_ist)
 
 		# Compensate for max heat rate to reduce overshoot
 		hold_scale = 1.0/self.heatrate_soll_set if self.heatrate_soll_set > 0 else 1.0