Advance simulation parity and 3-axis tutorial coverage

scripts/generate_browser_matrix_remediation.py

@@ -31,7 +31,12 @@ def digest(value: Any) -> str:
 
 def stable_output(value: str) -> str:
     """Remove browser diagnostic timestamps from repeatability evidence."""
-    return re.sub(r"\b\d{2}:\d{2}:\d{2}(?:\.\d+)?\b", "<time>", value)
+    normalized = re.sub(r"\b\d{2}:\d{2}:\d{2}(?:\.\d+)?\b", "<time>", value)
+    # Firefox installed through snap can emit a host-specific mount-namespace
+    # warning on stderr. It is not a browser result and its path/wording can
+    # differ between invocations, so retain only a deterministic marker.
+    normalized = re.sub(r"(?m)^update\.go:\d+: cannot change mount namespace.*$", "<environment-mount-diagnostic>", normalized)
+    return normalized
 
 
 def file_digest(path: Path) -> str | None: