Mech milestone phase 2: reconstruct HeatableSubsystem + map the roster hierarchy

HeatableSubsystem (HEAT.CPP) reconstructed + compile-verified (BT: 25 ok):
statics, ctor (chains MechSubsystem resource form + ResetToInitialState ->
currentTemperature=300, heatLoad=0), dtor, TestClass/TestInstance,
CreateStreamedSubsystem staged. Verified slice now: Subsystem -> MechSubsystem
-> HeatableSubsystem.

Also mapped the roster hierarchy from BT411, which is DEEPER than the staged
headers (recorded in MECHSUB.NOTES.md):
  MechSubsystem -> HeatableSubsystem -> HeatSink -> PoweredSubsystem -> {Sensor,
  Generator, ...}
Findings for the next steps: (1) HeatSink is MISSING entirely from the staged
tree and must be added between HeatableSubsystem and PoweredSubsystem;
(2) staged POWERSUB.HPP wrongly derives PoweredSubsystem from HeatableSubsystem
(real base = HeatSink) -- fix it; (3) PoweredSubsystem has inter-subsystem wiring
(resolves its voltage-source generator from the owner mech's subsystem roster),
imposing a segment-walk ordering constraint for the phase-4 ctor.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

restoration/source410/BT/HEAT.CPP

@@ -0,0 +1,120 @@
+//===========================================================================//
+// File:	heat.cpp                                                            //
+// Project: BattleTech           Brick: Mech subsystems                       //
+// Contents: HeatableSubsystem -- a MechSubsystem with a thermal state        //
+//---------------------------------------------------------------------------//
+// Copyright (C) 1995, Virtual World Entertainment, Inc.                     //
+// All Rights reserved worldwide                                             //
+// This unpublished sourcecode is PROPRIETARY and CONFIDENTIAL               //
+//===========================================================================//
+
+#include <bt.hpp>
+#pragma hdrstop
+
+#if !defined(HEAT_HPP)
+#	include <heat.hpp>
+#endif
+
+#if !defined(MECH_HPP)
+#	include <mech.hpp>
+#endif
+
+//
+//#############################################################################
+// Shared data support -- reuses the base Subsystem sets (no boot-critical
+// handlers / attributes of its own).
+//#############################################################################
+//
+Derivation
+	HeatableSubsystem::ClassDerivations(
+		MechSubsystem::ClassDerivations,
+		"HeatableSubsystem"
+	);
+
+HeatableSubsystem::SharedData
+	HeatableSubsystem::DefaultData(
+		HeatableSubsystem::ClassDerivations,
+		Subsystem::MessageHandlers,
+		Subsystem::AttributeIndex,
+		Subsystem::StateCount
+	);
+
+//
+//#############################################################################
+//#############################################################################
+//
+HeatableSubsystem::HeatableSubsystem(
+	Mech				*owner,
+	int					subsystem_ID,
+	SubsystemResource	*subsystem_resource,
+	SharedData			&shared_data
+):
+	MechSubsystem(
+		owner,
+		subsystem_ID,
+		(MechSubsystem::SubsystemResource *)subsystem_resource,
+		shared_data
+	)
+{
+	Check(owner);
+	Check_Pointer(subsystem_resource);
+	ResetToInitialState();
+	Check_Fpu();
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+HeatableSubsystem::~HeatableSubsystem()
+{
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+void
+	HeatableSubsystem::ResetToInitialState()
+{
+	Check(this);
+	currentTemperature	= 300.0f;
+	heatLoad			= 0.0f;
+}
+
+//
+//#############################################################################
+//#############################################################################
+//
+Logical
+	HeatableSubsystem::TestClass(Mech &)
+{
+	return True;
+}
+
+Logical
+	HeatableSubsystem::TestInstance() const
+{
+	return IsDerivedFrom(ClassDerivations);
+}
+
+//
+//#############################################################################
+// CreateStreamedSubsystem  Model-load-time construction (thermal resource +
+// damage-zone stream).  Not yet reconstructed (see MECHSUB.NOTES.md).
+//#############################################################################
+//
+int
+	HeatableSubsystem::CreateStreamedSubsystem(
+		NotationFile				*,
+		const char					*,
+		const char					*,
+		SubsystemResource			*,
+		NotationFile				*,
+		const ResourceDirectories	*,
+		int
+	)
+{
+	Fail("HeatableSubsystem::CreateStreamedSubsystem -- heat.cpp not yet reconstructed");
+	return 0;
+}

restoration/source410/BT/MECHSUB.NOTES.md

@@ -69,3 +69,39 @@ MechSubsystem must let the base Subsystem + DamageZone stream ctor handle armour
 Analysis complete; step 2 is the next code to write. This worksheet is the
 deliverable that keeps the subsystem foundation on the 4.10 damage model rather
 than BT411's divergent one.
+
+## Progress + roster hierarchy findings (2026-07-19)
+
+**DONE:** `MechSubsystem` base (MECHSUB.HPP/.CPP) and `HeatableSubsystem`
+(HEAT.HPP/.CPP) reconstructed + compile-verified. Verified vertical slice so far:
+`Subsystem → MechSubsystem → HeatableSubsystem`.
+
+**The subsystem hierarchy is DEEPER than the staged headers show.** From BT411:
+
+```
+MechSubsystem            (done)
+  └ HeatableSubsystem    (done; ctor chains MechSubsystem + ResetToInitialState
+                          -> currentTemperature=300, heatLoad=0)
+     └ HeatSink          (MISSING from the staged tree -- not in source410 nor
+                          CODE; VDATA HeatSinkClassID=0xBC5. Must be added.)
+        └ PoweredSubsystem (staged POWERSUB.HPP wrongly derives it from
+                          HeatableSubsystem -- real base is HeatSink; FIX the
+                          staged header. Also its ctor has embedded AlarmIndicators
+                          (electricalStateAlarm 5-level, modeAlarm 3-level) and a
+                          voltageSource SlotOf.)
+           └ Sensor       (surviving header CODE/BT/BT/SENSOR.HPP; leaf)
+           └ Generator, ... (other leaves)
+```
+
+**PoweredSubsystem has inter-subsystem wiring** — its ctor resolves a voltage
+source (generator) by indexing the OWNER MECH's subsystem roster
+(`owner->GetSubsystem(res->voltageSourceIndex)`), not the skeleton. So powered
+subsystems must be created AFTER the generator in the segment-walk order, and the
+Mech must expose GetSubsystemCount()/GetSubsystem(). This ordering constraint is
+a segment-walk (phase-4 ctor) concern; note it there.
+
+**Next roster steps:** add the missing HeatSink class (between HeatableSubsystem
+and PoweredSubsystem), fix POWERSUB.HPP's base, reconstruct PoweredSubsystem
+(with its alarms + voltage-source slot), then the leaves (Sensor first — its
+interface survives). Condenser/HeatWatcher (VDATA 0xBC6/0xBC7) are siblings in
+the heat family.