Make FSM hysteresis thresholds configurable

THRESH_HOLD_IDLE/HOLD_HEAT/IDLE_HEAT/IDLE_HOLD/HEAT_HOLD/HEAT_IDLE in
tc_constants.py were hardcoded module-level constants shared by every
controller instance, so tuning the IDLE/HOLD/HEAT hysteresis required
a code change.

Replace them with DEFAULT_THRESHOLDS plus an optional
TempCtrl.Thresholds config section, merged at construction time in
TempControllerBase.__init__ so configs that omit the section keep
behaving exactly as before. Documented the new section in
config.json.templ; left config.json.sim without it to exercise the
default-fallback path.

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

components/pid/tc_constants.py

@@ -8,12 +8,14 @@ class States(Enum):
 	HOLD = 2
 
 
-THRESH_HOLD_IDLE = 0.1
-THRESH_HOLD_HEAT = 1.0
-THRESH_IDLE_HEAT = 1.0
-THRESH_IDLE_HOLD = 0.1
-THRESH_HEAT_HOLD = 1.0
-THRESH_HEAT_IDLE = 1.0
+DEFAULT_THRESHOLDS = {
+	"HoldIdle": 0.1,
+	"HoldHeat": 1.0,
+	"IdleHeat": 1.0,
+	"IdleHold": 0.1,
+	"HeatHold": 1.0,
+	"HeatIdle": 1.0
+}
 
 
 class Test: