Golden gate: Linux baselines, canonical save, gate hardening (D521-D532)

Linux reference-frame set for all 21 levels and the cross-platform golden
rule (D521); golden tooling made non-destructive (D524); the gate pins a
canonical in-tree save (D529) and the PRNG seed (D532); the capture tool's
per-level re-pin bug fixed and the Linux set re-captured under the
canonical save (D530, D531); no-arg verify.sh exits non-zero. README and
docs visual/consolidation passes; the 15 MB preview gif replaced by stills.

Refs: D521 D523 D524 D525 D526 D527 D528 D529 D530 D531 D532

tools_pc/p7_report.py

@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+# P7 (2026-10-04): cross-platform golden table.
+# For every level, compare tools_pc/golden/<level>/linux/ against
+# tools_pc/golden/<level>/win/ with framediff.py in both modes:
+#   --exact --tol 2          -> per-pixel share over tol (the rendering delta)
+#   default (structural)     -> worst grid-cell dmean, nonclear delta, phash
+# Prints one line per (level, frame) plus a per-level verdict.
+#
+# Path-agnostic: the repo root is the parent of this script's directory
+# (tools_pc/), so it can be invoked from anywhere; no absolute path, no
+# '~', no machine default.
+import os
+import subprocess
+import json
+
+ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+FD = os.path.join(ROOT, "tools_pc", "framediff.py")
+
+LEVELS = [("dam","33"),("facility","34"),("runway","35"),("surface1","36"),
+          ("bunker1","09"),("silo","20"),("frigate","26"),("surface2","43"),
+          ("bunker2","27"),("statue","22"),("archives","24"),("streets","29"),
+          ("depot","30"),("train","25"),("jungle","37"),("control","23"),
+          ("caverns","39"),("cradle","41"),("aztec","28"),("egypt","32"),
+          ("cuba","54")]
+
+def run(args):
+    p = subprocess.run(args, capture_output=True, text=True)
+    out = p.stdout + p.stderr
+    i = out.find("{")
+    if i < 0:
+        return None, p.returncode, out
+    try:
+        d, _ = json.JSONDecoder().raw_decode(out[i:])
+    except Exception:
+        return None, p.returncode, out
+    return d, p.returncode, out
+
+rows = []
+for name, num in LEVELS:
+    lin = os.path.join(ROOT, "tools_pc", "golden", name, "linux")
+    win = os.path.join(ROOT, "tools_pc", "golden", name, "win")
+    ex, rcx, ox = run(["python3", FD, lin, "--golden", win,
+                       "--exact", "--tol", "2", "--json"])
+    st, rcg, og = run(["python3", FD, lin, "--golden", win, "--json"])
+    if ex is None or st is None:
+        rows.append((name,"ERR","framediff failed", rcx, rcg))
+        continue
+    per = {}
+    for r in ex["results"]:
+        per.setdefault(r["frame"], {})["exact"] = r
+    for r in st["results"]:
+        per.setdefault(r["frame"], {})["struct"] = r
+    for f in sorted(per):
+        e = per[f].get("exact", {}); s = per[f].get("struct", {})
+        rows.append((name, f.replace("frame_",""),
+                     "%.3f%%" % e.get("diff_pct", 0.0),
+                     str(s.get("worst_cell","")), str(s.get("phash_hamming","")),
+                     e.get("status",""), s.get("status","")))
+    print("%-9s exact rc=%d struct rc=%d" % (name, rcx, rcg))
+
+print()
+print("level      frame   over%   worst_cell phash exact struct")
+for r in rows:
+    if len(r) == 7:
+        print("%-10s %-6s %7s %10s %5s %6s %6s" % r[:7])
+    else:
+        print("%-10s %s" % (r[0], r[1]))