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/decomp-reference.md

@@ -163,6 +163,10 @@ The authentic stack is DEFAULT-ON (`BTEnvOn`, mechrecon.hpp): `BT_GAIT_CUTOVER`,
 | `BT_AIM_LOG` | `[pick]` ray/box/hit diagnostics (Mech::PickRayHit) |
 | `BT_FIRE_ARC=<deg>` | OPT-IN external-camera fire-arc clamp (unset = authentic no-arc) |
 | `BT_START_INSIDE` | begin in the cockpit view (V toggles) |
+| `BT_FORCE_MODEL=<name>` | force the player mech (`madcat`/`owens`/…; btl4mssn.cpp — per-mech cockpit bring-up) |
+| `BT_HIDE_COCKPIT` | hide the `*_cop` canopy shell (SHOWS by default — see [[cockpit-view]]) |
+| `BT_COP_*` / `BT_EYE_FWD=<f>` | cockpit canopy + eye diagnostics (`DOUBLE`/`FLIP`/`RAMP_L`/`DEBUG`/`DUMP`; eye forward-push probe) — [[cockpit-view]] |
+| `BT_SHOT=<path.png>` | periodic backbuffer dump (every 90 frames) — non-disruptive visual verification |
 | `BT_TLOC_LOG` | translocation-warp lifecycle log (`[tloc] warp COLLAPSE/EXPAND/phase=…`) |
 | `BT_WARP_*` | translocation-warp visual tuning — all default to the verified values (see [[translocation-warp]]): `EYE_UP=8.25` (on-axis), `SPIN=4`, `TWIST=0`, `CONTRAST=1.0`, `LO_*/HI_*` (lavender ramp), `BLUR=0`, `TESS=3`, `MIP=1`, `CULL=cw`, `ANISO=0` |
 | `BT_WARP_SELFTEST` / `BT_WARP_SELFSHOT=<prefix>` | DIAG (off by default): force a held warp in a solo game / dump backbuffer frames to disk (visual-verification harness) |
@@ -173,6 +177,17 @@ BT_PUNCH, …) are catalogued in [[rendering]]. Warp visuals: [[translocation-wa
 **Translocation-warp addresses** [T1]: `POVTranslocateRenderable` = L4VIDRND.cpp:1749 / .h:638; its
 per-frame Execute (spin about local Z + submit, NO texcoord/ramp work) = **`FUN_00453dc4`**
 (`reference/decomp/all/part_007.c`), using axis-rotation helper `FUN_0040998c` (axis idx 2 = Z).
+
+**Cockpit-eye / punch addresses** [T1] (full story: [[cockpit-view]]): eye ctor
+**`FUN_004579a8`** (part_007.c:9274 = DPLEyeRenderable; offset = segment `GetBaseOffset`
+segment+0x74, parent = parent-segment DCS; caller part_014.c:5525-66 gates on `"siteeyepoint"`);
+matrix multiply **`FUN_0040b104(dst,A,B)` = `B × A`** (translation from B — operand-order trap!);
+euler→rotation `FUN_0040ac6c`; per-frame view **`FUN_004c22c4`** (part_013.c:11742): eyeWorld from
+the live view-DCS then **`FUN_0040b244` = affine INVERSE** → VIEW (+ uniform zoom) — NO LookAt;
+eye euler-change refresh `FUN_00457b48` (part_007.c:9360). Punch: **`dpl_Punchize` =
+`FUN_00490308`** (part_011.c:6219) → `FUN_0048e5b0` → `FUN_00492580(0x20,…)` board send, constant
+tokens `{0x80000003,0x80000017,0x80000004}` (sibling `dpl_Damagize` `FUN_004902b0` = same cmd,
+different triple); SV_SPECIAL PUNCH dispatch part_011.c:10209/10252 → callback LAB_004596ac.
 Respawn SIM path: `DropZoneReply` `FUN_004bffd0` → `Mech::Reset` @0x4009fb74; `CreatePlayerVehicle`
 `FUN_004bfcac`. See [[translocation-warp]], [[multiplayer]].