Vendor dpl3-revive: the Division/DPL3 renderer, now ours

Bring the graphics-dev collaborator's dpl3-revive into the repo as first-class
project code (they've handed it off; it's ours now). This is the proven
Division renderer that our in-process rt_draw has been trying to be.

What's here:
- parser/  B2Z/V2Z/SVT/SCN/SPL/BGF/BMF/BSL decoders (pure Python).
- spec/    reverse-engineered format + the definitive VelociRender wire
           protocol (from the original DIVISION source, matches our live
           VPX node/action tables exactly).
- source-ref/  read-only copies of the original DIVISION C (BIZREAD.C,
           DPLTYPES.H, DPL.H) that define the formats.
- patha/   the "virtual VelociRender board": vrboard.py (24-action protocol
           server), vrview.py (numpy software rasterizer, the reference),
           vrview_gl.py (moderngl GPU backend, 832x512@60Hz), plus the
           run/replay/regress tooling and evidence renders. Drives FLYK/BLADE/
           Star Trek demos AND our btl4opt/rpl4opt game binaries.
- viewer/  WebGL archive generators (.py); prebuilt HTML/data regeneratable.
- samples/ small test models/textures.
- bt*.raw.bin  real BTL4OPT arena wire captures (kept for offline renderer
           testing/regression against OUR game).

.gitignore keeps the multi-hundred-MB demo capture dumps + debug logs +
regeneratable viewer bundles out of history (they stay on disk).

Phase 0 of the integration is validated: their board decodes our bt8 capture
with zero errors (3748 nodes, 507 instances, 4 mechs) and renders our arena
(terrain/dome/sky, correct Division DAC gamma). Plan + status in memory;
integration continues in emulator/RENDERER-COLLAB.md.

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

dpl3-revive/patha/debug_view.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+"""debug_view.py -- numeric check of vrview transforms against a capture replay."""
+import os, sys, struct
+import numpy as np
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+os.environ.setdefault('SDL_VIDEODRIVER', 'dummy')
+from vrboard import VirtualBoard, Assembler
+from decode_anim import find_framed_start
+from vrview import Renderer, _mat_from_dcs
+
+path = sys.argv[1] if len(sys.argv) > 1 else 'cap5.raw.bin'
+data = open(path, 'rb').read()
+board = VirtualBoard()
+asm = Assembler(); asm.feed(data[find_framed_start(data):])
+for m in asm:
+    try: board.handle(m)
+    except Exception: pass
+    if board.frames >= 600: break
+
+r = Renderer(); r.cache.maybe_rebuild(board)
+c = r.cache
+print('cam chain', [hex(h) for h in c.cam_chain])
+for h in (0x1, 0x2, 0x3):
+    b = board.nodes.get(h, {}).get('body') or b''
+    if len(b) >= 76:
+        M = _mat_from_dcs(b)
+        print(f'dcs {h:#x} diag={np.diag(M)[:3]} row3={M[3,:3]} anim={h in board.anim}')
+V = np.linalg.inv(r.chain_matrix(board, c.cam_chain))
+print('V row3 (eye offset):', V[3, :3])
+
+for inst in c.instances:
+    M = r.chain_matrix(board, inst['chain'])
+    for gh in inst['geoms']:
+        mesh = c.meshes[gh]
+        pw = mesh['pos'] @ M[:3, :3] + M[3, :3]
+        pe = pw @ V[:3, :3] + V[3, :3]
+        z = -pe[:, 2]
+        vis = z > 8
+        if vis.any():
+            xp = pe[vis, 0] * 1.3 / z[vis]; yp = pe[vis, 1] * 1.3 / z[vis]
+            scr = f"proj x[{xp.min():7.2f},{xp.max():7.2f}] y[{yp.min():7.2f},{yp.max():7.2f}]"
+        else:
+            scr = "behind camera"
+        print(f"dcs={inst['chain'][0]:#04x} geom={gh:#04x} v={len(pw):4d} "
+              f"world y[{pw[:,1].min():8.1f},{pw[:,1].max():8.1f}] "
+              f"size={np.ptp(pw,0).round(0)} {scr}")