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>

CLAUDE.md

@@ -69,6 +69,7 @@ precise than anything you can infer.
 | Damage zones, targeting, firing, death | `context/combat-damage.md` |
 | Rendering, LODs, materials, sky, shadows, beams | `context/rendering.md` |
 | The death/respawn translocation warp (tsphere vortex) | `context/translocation-warp.md` |
+| First-person cockpit canopy (*_cop) + the eyepoint camera | `context/cockpit-view.md` |
 | Cockpit gauges / MFD HUD | `context/gauges-hud.md` |
 | Multiplayer, replication, netcode | `context/multiplayer.md` |
 | Pod hardware, monitors, RIO, MFD surfaces | `context/pod-hardware.md` |