Anchor the forecast to the real current temperature, not a cold start

send_forecast() was defaulting to a cold start at ambient (SudForecastEstimator.
estimate()'s default when start_theta isn't passed), so the forecast's t=0
never matched whatever temperature the pot actually was at - understating
how long the first ramp would really take whenever it wasn't already cold.

Anchoring at tc.get_theta_ist() seemed like the obvious fix but isn't
reliable right after Load: that's only ever updated inside process(), which
a model-based controller (Smith) doesn't run until its plant params are
configured - which now only happens once a Sud is loaded (see the
"inert until loaded" change) - so theta_ist can still be sitting at its
never-updated __init__ default of 0 the instant send_forecast() reads it.
Added TempControllerBase.get_theta_ist_set() (mirroring the existing
get_theta_soll_set()) - the raw sensor reading, updated the instant a
reading comes in regardless of whether process() has ever run - and used
that instead.

That still leaves a gap between Load and Start: the real temperature can
drift (time passing, manual heating via the Manual tab) between loading a
schedule and actually starting it, leaving the forecast anchored to a
now-stale temperature. recv()'s 'Start' handler now re-sends the forecast,
freshly anchored to the real temperature at that moment, on every fresh
start (not a Pause->resume, which keeps the already-established forecast
rather than discarding it mid-run).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DkkuG48uHFCGKe6dPSERFk

components/pid/temp_controller_base.py

@@ -97,6 +97,17 @@ class TempControllerBase(APid):
 	def get_theta_ist(self):
 		return self.theta_ist
 
+	def get_theta_ist_set(self):
+		"""The raw sensor reading, as last pushed via set_theta_ist() -
+		unlike get_theta_ist() (self.theta_ist), this is updated the
+		instant a reading comes in, regardless of whether process() has
+		ever actually run (e.g. before set_params()/a model-based
+		controller's plant params have been configured - see SudTask.
+		send_forecast(), which needs a real "current temperature" at the
+		moment a Sud is loaded, before this controller may have ticked
+		even once)."""
+		return self.theta_ist_set
+
 	def set_heatrate_ist(self, value):
 		self.heatrate_ist_set = value