Cockpit: authentic eyepoint + canopy lattice render (task #55)

The first-person cockpit now shows by default and matches gameplay footage
(verified on the Madcat). Two decomp-verified reconstructions:

EYEPOINT (FUN_004579a8 + caller part_014.c:5525, FUN_004c22c4):
- eye offset = siteeyepoint GetBaseOffset (not GetSegmentToEntity, not the
  upright hack), parented on the PARENT segment DCS (btl4vid.cpp)
- live view = affine INVERSE of the eye world matrix (L4VIDRND Execute) --
  replaces the hand-rolled LookAtRH whose +Z-forward/+Y-up row guess aimed
  some mechs into the canopy; combine order fixed to baseOffset * R
- chase camera basis + aim boresight re-expressed for the inverse convention
  (row2 = back); boresight now derives from the view matrix (the stale rows
  aimed the pick ray at the sky = no target, no discharge)

CANOPY (*_COP.BGF, dpl_Punchize geogroups):
- every shell is an open strut lattice (38-59% boundary edges, all 12 mechs);
  rendered single-sided with per-face INWARD winding (l/r torso patches are
  mirrored, so no global winding works) the struts are the dark frame and the
  openings show the world
- frame colour = the 'softer' ramp near its dark end (texture-less unlit ramp;
  BLXSKIN.BMF has no texture -- the old "punch texels" theory was wrong)
- scoped by filename (meshIsCop); wrong drop-punch + view-cut paths removed
- BT_FORCE_MODEL=<name> forces the player mech for per-mech bring-up

KB: new context/cockpit-view.md topic; punch split corrected in bgf-format;
gotchas 14 (LookAt axis guess) + 15 (per-patch edge namespaces); env gates +
eye/punch addresses in decomp-reference.

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

context/bgf-format.md

@@ -43,8 +43,18 @@ LOD whose band contains the camera distance.
 - **ADDITIVE_LODS** (object-level `SV_SPECIAL` token, 135 pod BGFs — all arena structures): at eye
   distance d, EVERY LOD with `d < OutDist` draws (near detail ADDS onto coarser massing). Non-additive
   keep first-LOD-only (the 2007 engine's own behavior). [T2]
-- **PUNCH** (patch-level `SV_SPECIAL`): cutout geogroups — black texels = HOLES (alpha-test in the
-  opaque pass). Coplanar shells inside one LOD z-fight → depth-bias by submission ordinal. [T2]
+- **PUNCH** (patch-level `SV_SPECIAL`, `dpl_Punchize` = FUN_00490308 → VPX board cmd `0x20`, tokens
+  `{0x80000003,0x80000017,0x80000004}` — a CONSTANT geogroup-modifier opcode, no color key; the
+  sibling `dpl_Damagize` FUN_004902b0 uses the same cmd with a different triple). Two cases: [T1]
+  - **Textured** punch (arena walls/catwalks): black texels = HOLES (alpha-test in the opaque
+    pass). Coplanar shells inside one LOD z-fight → depth-bias by submission ordinal. [T2]
+  - **Texture-less** punch (the `*_cop` cockpit canopies: blakskn + `softer` ramp, NO texture tag
+    in the BMF — byte-verified, 238-byte BLXSKIN.BMF): the frame/window split is the GEOMETRY —
+    every `_cop` is an open strut lattice (38-59% boundary edges, all 12 mechs); rendered
+    single-sided with per-face INWARD winding orientation (the l/r torso patches are MIRRORED, so
+    no single global winding works) the struts are the dark frame and the openings show the world.
+    The old "canopy windows are punch texels" claim was WRONG — there is no texel to key. See
+    [[cockpit-view]]. [T2 render-verified in-game on Madcat vs gameplay footage]
 
 ## Shading model (from libDPL DPLTYPES.H)
 Shading is selected PER-GEOMETRY by vertex type: