#110: the zone destruction cascade is LIVE -- an arm now takes its gun pod with it

Lynx: "You can destroy an upper arm, and the gun pod is intact and can still
fire."  Conn Man's audit: three chassis, both arms, reproducible.  And the user
is right that this family was claimed fixed before: #86 gated fire on the
WEAPON's own destruction and was verified by destroying the weapon directly
(BT_KILL_SUBSYS) -- the field scenario was the ARM ZONE dying with the weapon
subsystem healthy, which that bench never reproduced.  Oracle's 693-night "I can
still fire destroyed energy weapons" was almost certainly this mechanism.

ROOT CAUSE -- a silent stub.  Mech__DamageZone::RecurseSegmentTable @0049cad4
was transcribed faithfully... against three local shim types whose iterators
unconditionally return NULL:
    struct SegmentIterator { DZRef *Next() { return 0; } };
    struct SegTableX       { SegmentRecord *operator[](int) { return 0; } };
The cascade fired on zone death (bench: 72 [cascade] lines), "descended", and
touched nothing.  Every line read correct; none of it did anything.

THE REAL WALK (decomp re-read, FUN_0049cad4): iterate the mech's segment table
(mech+0x300, vtbl+0x34 GetNth) to this zone's segment, then
    destroySiblingsOnDestruction (Wword 0x68): recurse every other zone on the
        SAME segment (seg+0xD0), setting graphic state 2 (Gone)
    descendOnDestruction (Wword 0x67): recurse every zone on every CHILD
        segment (seg+0xE8 -> child+0xD0) -- the arm takes the gun
The engine ALREADY HAS both structures: EntitySegment::damageZoneTable @0xD0 /
childIndexTable @0xE8 (TableOf is 0x18 -- byte-identical to the decomp offsets),
populated at stream time by JMOVER.cpp:373 [T0].  The stub was never necessary.
Implemented with the engine iterators via two new read accessors on
EntitySegment (SEGMENT.h); the binary's asymmetry is reproduced as-is (the
sibling loop checks graphic state != 1, the child loop does not; re-hits on a
1.0 zone re-run the cascade -- idempotent in effect).

VERIFIED (ava1, self-damage to one zone, autofire everything):
  dz_rarm -> [cascade] zone 9 -> zone 17; AFC100 + AmmoBinAFC100 + Condenser6
      ForceCriticalFailure'd; "[ammo] AFC100 -> NoAmmo (gate1): destroyed=1";
      torso LRM5/SRM2 keep firing (correct)
  dz_larm -> [cascade] zone 2 -> zone 6; PPC + Condenser4 force-failed;
      "[emitter] 'PPC' fire REFUSED (destroyed=1)" x4998 -- the emitter gate now
      logs refusals BY NAME (the FIRED line never named its weapon, which is how
      #86's verification gap survived)
  regression smoke: frame time 7.13/7.20ms, 0 asserts, 0 cascades in ordinary
      combat (they fire only on genuine zone deaths)

Authored data (now dumped under BT_DMG_LOG): descend=1 on exactly the four arm
zones (ava1: 2/6/9/17), destroySibs=0 everywhere -- so legs/torso behavior is
untouched by this change.

KB: combat-damage.md cascade section; reconstruction-gotchas #26 (the
silent-stub trap: a shim that returns EMPTY converts a reconstruction into
fiction that reads correct -- shims must Fail() loudly or log their emptiness).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

engine/MUNGA/SEGMENT.h

@@ -126,6 +126,17 @@ protected:
 // Accessors
 //
 public:
+	// #110 (BT reconstruction): read access to the two streamed tables the
+	// binary's zone-destruction cascade walks (Mech__DamageZone::
+	// RecurseSegmentTable @0049cad4 -- seg+0xD0 damage zones, seg+0xE8 child
+	// indices).  Read-only; population stays with JointedMover streaming.
+	IntegerTable&
+		GetDamageZoneTable()
+			{Check(this); return damageZoneTable;}
+	IntegerTable&
+		GetChildIndexTable()
+			{Check(this); return childIndexTable;}
+
 	void
 		ModifySegment(Logical modified = True)
 			{Check(this); segmentModified = modified;}