Make Sud steps ramp based on the actual temperature gap, not a 'ramp' key

Previously, whether a schedule step ramped at all was decided purely by
the presence of a 'ramp' key (components/sud.py's _advance()) - a
hold-only step jumped straight into its hold countdown, assuming the
plant was already at temperature. Now every step ramps toward
'temperature' first, for as long as the controller's own gap-tracking
FSM (TempControllerBase, already distinguishing HEAT/COOL/HOLD) says
the gap actually warrants it - via the new is_holding() (on APid and
TempControllerBase), which replaces a separate, redundant
TEMP_REACHED_TOLERANCE constant duplicated across tasks/sud.py,
components/sud_forecast.py, and scripts/demos/sud/demo_sud.py.

set_theta_soll() now recomputes the FSM eagerly so is_holding() can't
read stale HOLD for a tick after a much-further-away target is pushed.

components/sud.py's _build_step() always synthesizes a 'ramp' block
from default.step.ramp (so 'rate' is always available), but leaves
'temperature' undefaulted - every real sude/*.json's
default.step.temperature is inert template filler, and defaulting it
would send hold-only steps chasing 0 degrees. SudTask/
SudForecastEstimator/the demo only push a new theta_soll/heatrate_soll
when a step actually specifies its own temperature; otherwise the
controller keeps whatever the previous step left running.

Also fixes a related crash this surfaced: SudTask.remaining_schedule()'s
synthetic mid-hold step dropped 'ramp' to signal "don't re-ramp" - now
that every step always carries a 'ramp' dict, dropping it left 'rate'
missing the moment the synthetic step was re-resolved by
SudForecastEstimator. Drops 'temperature' instead, which is what
actually signals "no new target" under the new model.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LhiQe64F74uHV8jzuoSa5K

components/sud_forecast.py

@@ -2,12 +2,6 @@ from components.plant import Pot
 from components.pid import PidFactory
 from components.sud import Sud, SudState
 
-# Real schedules need real time to spin up each ramp and settle within this
-# tolerance before "reached" fires - matching tasks/sud.py's
-# TEMP_REACHED_TOLERANCE exactly is what makes this simulation's predicted
-# duration line up with the real run's.
-TEMP_REACHED_TOLERANCE = 0.2
-
 # Safety cap so a schedule whose target a step can never actually reach
 # (e.g. a "hold" colder than ambient with no active cooling) can't hang the
 # simulation forever - the estimate is simply cut off there.
@@ -65,10 +59,9 @@ class SudForecastEstimator:
 			pot.set_thermal_params(params['M'], params['C'])
 			if hasattr(tc, 'set_model_params'):
 				tc.set_model_params(params['M'], params['C'])
-			ramp = step.get('ramp')
-			if sud.state == SudState.RAMPING and ramp is not None:
+			if sud.state == SudState.RAMPING and step['temperature'] is not None:
 				tc.set_theta_soll(step['temperature'])
-				tc.set_heatrate_soll(ramp['rate'])
+				tc.set_heatrate_soll(step['ramp']['rate'])
 		sud.set_on_changed('step', on_step_changed)
 
 		t = [0.0]
@@ -83,7 +76,7 @@ class SudForecastEstimator:
 			pot.set_power(max(0, self.heater_max_power * tc.get_power()))
 
 			if sud.state == SudState.RAMPING:
-				if abs(tc.get_theta_ist() - tc.get_theta_soll_set()) < TEMP_REACHED_TOLERANCE:
+				if tc.is_holding():
 					sud.temp_reached()
 			elif sud.state == SudState.WAIT_USER:
 				# A real user's confirm time isn't predictable - count it