handoff: #91 decode (own missile pod, blakskn material-key fix)

scratchpad/SESSION_HANDOFF_20260803.md

@@ -210,3 +210,18 @@ btl4lobby.cpp, ~60 lines, in the 717 cut):
   STEAM UNAVAILABLE, LEFT BEHIND (no token in btl4map). Old exes still
   quit silently on rejection (unfixable in the field); host roster
   marker is the operator's view. content/btl4.exe = 4.11.756 (648f6b1).
+
+### #91 thor "black rectangle": ROOT-CAUSED + FIXED (2026-08-04)
+Ronin's report (3rd sighting) pinned it: the rectangle = the thor's OWN
+thx_msl missile-pod mount plate. The inside view is a per-mech AUTHORED
+type-A set (KB "exactly one mesh" claim corrected in cockpit-view.md):
+thor = cop+tor+MSL, owens = cop+BOTH LEGS+tshd, sunder/loki/avatar =
+cop+tor. Pilot-facing surfaces are <pfx>skin:blakskn_dz_* -- the same
+interior-structure material as the canopy frame -- but the unlit frame
+constant keyed on the _cop FILENAME, so pod/legs rendered void (0,0,0)
+instead of (0.13,0.12,0.15). bgfload now keys on the material family
+(mechfx shadow quads excluded). Verified by walking captures (zero
+pure-black lower-band px; plate blends with the frame bar at rest).
+Diags: BT_MAT_LOG, BT_HIDE_INSIDE_SEG, [view] roster names; bench
+scratchpad/night11/thorrect.sh. #91 labeled awaiting-verification --
+Ronin should re-fly the thor on 717.