VDB: dump captured palettes (VDB_PALDUMP) + swatch renderer

VDB_PALDUMP=<prefix> writes each completed 768-byte palette load to
<prefix>N.rgb (256 RGB entries per VDB display group). render_vdb_palettes.py
renders each as a 16x16 swatch grid + linear ramp.

First capture: pal1 (aux1) is a structured red/green/olive/black color map
(2-bit R x 2-bit G) -- likely the color display's status coloring; pal0
(secondary, dynamic ~29 reloads) and pal2 (aux2) are grayscale, sampled black
mid-animation. Palettes are the per-display color maps the VDB applies when
splitting the framebuffer to the six monitors.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

emulator/render_vdb_palettes.py

@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+"""Render captured VDB palettes (VDB_PALDUMP <prefix>N.rgb) as swatch images.
+
+Each .rgb is 256 RGB triplets (768 bytes) -- one of the VDB's three display
+palette groups (secondary / aux1 / aux2). For each, emit:
+  <prefix>N.png  -- a 16x16 grid of the 256 colors + a 256-wide linear ramp.
+
+Usage: render_vdb_palettes.py <prefix>   (e.g. .../scratchpad/vdbpal)
+"""
+import sys
+
+from PIL import Image, ImageDraw, ImageFont
+
+NAMES = {0: "secondary (dynamic)", 1: "aux 1", 2: "aux 2"}
+
+
+def render_one(path, out, title):
+    data = open(path, "rb").read()
+    if len(data) < 768:
+        data = data + b"\x00" * (768 - len(data))
+    cols = [(data[i * 3], data[i * 3 + 1], data[i * 3 + 2]) for i in range(256)]
+
+    cell, grid = 28, 16
+    gw = cell * grid
+    ramp_h = 40
+    pad, top = 12, 34
+    W = gw + pad * 2
+    H = top + gw + 10 + ramp_h + pad
+    img = Image.new("RGB", (W, H), (24, 24, 28))
+    d = ImageDraw.Draw(img)
+    try:
+        font = ImageFont.truetype("consola.ttf", 16)
+    except Exception:
+        font = ImageFont.load_default()
+    d.text((pad, 8), title, fill=(230, 230, 235), font=font)
+
+    # 16x16 swatch grid (index 0 top-left, row-major)
+    for i, c in enumerate(cols):
+        x = pad + (i % grid) * cell
+        y = top + (i // grid) * cell
+        d.rectangle([x, y, x + cell - 1, y + cell - 1], fill=c)
+    # linear ramp strip below
+    ry = top + gw + 10
+    for i, c in enumerate(cols):
+        x0 = pad + i * (gw / 256.0)
+        x1 = pad + (i + 1) * (gw / 256.0)
+        d.rectangle([x0, ry, x1, ry + ramp_h], fill=c)
+    d.rectangle([pad, ry, pad + gw, ry + ramp_h], outline=(80, 80, 88))
+    img.save(out)
+    # quick stats
+    grays = sum(1 for r, g, b in cols if abs(r - g) < 6 and abs(g - b) < 6)
+    print(f"{out}: {grays}/256 grayscale-ish entries")
+
+
+def main():
+    prefix = sys.argv[1]
+    for g in (0, 1, 2):
+        p = f"{prefix}{g}.rgb"
+        try:
+            render_one(p, f"{prefix}{g}.png",
+                       f"VDB palette {g} - {NAMES.get(g, '')}")
+        except FileNotFoundError:
+            print(f"(no {p})")
+
+
+if __name__ == "__main__":
+    main()