Wreck sink (quadratic burial) + ldbr debris field -- the 1996 script completed

Answers "does the wreck fade away?": YES, by sinking.  FUN_00456410 (the 1996
sink renderable) computes offsetY = rate * t^2; the hulk's authored rate is
-0.025 -> the ~7-unit hulk is fully underground ~17s after the kill.  The
script also pairs the standing hulk with the LDBR strewn-debris field (12x13u
flat scatter), parented together and sinking together.

Also verified from the mesh data: BLHDBR (1537 verts -- more than the intact
torso) IS the authored Blackhawk wreck: the classic standing-leg-in-rubble
sculpt.  The "just a leg standing there" report is the authentic art.
(THRDBR -- the mesh the 1996 script hardcoded -- parses to ZERO vertices;
more evidence the hardcode was an unfinished dev shortcut.)

Implementation: SwapToWreck adds the ldbr piece; TickWreck applies the
quadratic sink per frame (driven from the dead mech's UpdateDeathState),
hides both pieces at burial and reports it so the wreck-smoke re-arm stops
with the wreck.  DPLStaticChildRenderable::SetOffsetTranslation added
(Execute re-reads OrientationMatrix per frame -- same in-place idiom as
SetDrawObj).

Lifecycle verified live: kill -> 'blhdbr.bgf' + ldbr debris -> smoke re-arm
@10s -> wreck buried @~17s -> smoke stops.

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

scratchpad/bgfbounds.py

@@ -0,0 +1,47 @@
+import struct, sys
+
+VTX_TAGS = {0x80: 12, 0x81: 24, 0x82: 28, 0x88: 20, 0x89: 32, 0x8A: 36}
+CONTAINERS = {0x03, 0x40, 0x41, 0x42, 0x46, 0x48, 0x70}  # HEADER OBJECT LOD PATCH PMESH SPHERE_LIST BOUND
+
+def bounds(path):
+    data = open(path, 'rb').read()
+    assert data[:8] == b'DIV-BIZ2', path
+    lo = [1e9, 1e9, 1e9]
+    hi = [-1e9, -1e9, -1e9]
+    nverts = 0
+
+    def walk(pos, end):
+        nonlocal nverts
+        while pos < end - 2:
+            tagword, = struct.unpack_from('<H', data, pos)
+            tag = tagword & 0x2fff
+            wide = (tagword >> 14) & 3
+            if wide == 1:
+                ln, = struct.unpack_from('<H', data, pos + 2)
+                hdr = 4
+            else:
+                ln = data[pos + 2]
+                hdr = 3
+            payload = pos + hdr
+            if tag in VTX_TAGS:
+                stride = VTX_TAGS[tag]
+                n = ln // stride
+                for i in range(n):
+                    x, y, z = struct.unpack_from('<3f', data, payload + i * stride)
+                    for a, v in enumerate((x, y, z)):
+                        if v < lo[a]: lo[a] = v
+                        if v > hi[a]: hi[a] = v
+                nverts += n
+            elif tag in CONTAINERS:
+                walk(payload, payload + ln)
+            pos = payload + ln
+    walk(8, len(data))
+    print('%-14s verts=%5d  X[%7.2f %7.2f]  Y[%7.2f %7.2f]  Z[%7.2f %7.2f]'
+          % (path.split('\\')[-1], nverts, lo[0], hi[0], lo[1], hi[1], lo[2], hi[2]))
+
+base = r'C:\git\bt411\content\VIDEO\GEO\%s'
+for f in ['LDBR.BGF', 'MDBR.BGF', 'FLAMESML.BGF', 'FLAMEBIG.BGF']:
+    try:
+        bounds(base % f)
+    except Exception as e:
+        print(f, 'ERR', e)