tools(verify): fast/medium/full verification tiers with a compiled-in source stamp (L39); research R6

BuildLinux.sh hashes a sorted manifest of compiled inputs into VOXELFORGE_SOURCE_STAMP, printed first by
every executable; Standalone/Tools/verify/verify.py checks it before and after each tier and records
binary/input hashes and the resolved recipe, style map and layout. Fast (163 s) runs on the canonical owner
world only and asserts FI Style 2 / SW Style 1; medium (8 min) and full (26 min) add the style matrix,
GCC, determinism and cost. Controls: stale source, mislabelled style-0 owner, all-black capture, L30/L31,
L35/L36 and the L38 step are all rejected. No geometry change; owner hashes identical to L37.
Research R6: leak table, generator contract and a 10-step metre-native migration plan.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Tools/verify/capture_quality.py

@@ -0,0 +1,54 @@
+#!/usr/bin/env python3
+"""Reject empty and nearly black captures by decoding pixels and measuring coverage."""
+from __future__ import annotations
+
+import argparse
+import math
+from pathlib import Path
+import subprocess
+import sys
+
+
+LIMIT = ["taskset", "-c", "0-11", "prlimit", "--as=6442450944", "--"]
+
+
+def inspect(path: Path) -> tuple[bool, str]:
+    probe = subprocess.run([*LIMIT, "timeout", "30s", "ffmpeg", "-nostdin",
+        "-hide_banner", "-loglevel", "error", "-i", str(path), "-frames:v", "1",
+        "-f", "rawvideo", "-pix_fmt", "rgb24", "pipe:1"],
+        stdout=subprocess.PIPE, stderr=subprocess.PIPE, timeout=30, check=False)
+    if probe.returncode != 0 or not probe.stdout or len(probe.stdout) % 3:
+        return False, f"decode_failed exit={probe.returncode} bytes={len(probe.stdout)}"
+    raw = probe.stdout
+    count = len(raw) // 3
+    total = 0
+    square_total = 0
+    covered = 0
+    for index in range(0, len(raw), 3):
+        luminance = (77 * raw[index] + 150 * raw[index + 1] + 29 * raw[index + 2]) >> 8
+        total += luminance
+        square_total += luminance * luminance
+        covered += luminance > 12
+    mean = total / count
+    variance = max(0.0, square_total / count - mean * mean)
+    deviation = math.sqrt(variance)
+    coverage = covered / count
+    passed = deviation >= 2.0 and coverage >= 0.001
+    return passed, (f"pixels={count} mean_luma={mean:.3f} stddev_luma={deviation:.3f} "
+                    f"coverage_luma_gt12={coverage:.5f} thresholds=(stddev>=2.0,coverage>=0.001)")
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("image", type=Path)
+    args = parser.parse_args()
+    if not args.image.is_file():
+        print(f"[CaptureQuality] image={args.image} status=FAIL reason=missing")
+        return 1
+    passed, detail = inspect(args.image)
+    print(f"[CaptureQuality] image={args.image} {detail} status={'PASS' if passed else 'FAIL'}")
+    return 0 if passed else 1
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())