[CI] (.github/workflows, scripts/ci, tools/trace_replay): check the verify control's reason in one script

- scripts/ci/retrace_verify_reason.py holds the retrace-verify control's reason check, a plain search for Fatal{PipeVerifyDiffer, "GetRenderStateParameters@ (run_trace_case.cmake prints the library log through message(STATUS), which never re-wraps, so the old prefix stripping and whitespace collapse are gone); the workflow step and test_run_trace_case.py both run it, so the test can no longer pass on a copy
- canned reds carrying a different Fatal (Fatal{UnmigratedPipeInput, "GetPixelStoreParameters@ReadPixels"}) or the comparator's divergence on another field (Fatal{PipeVerifyDiffer, "GetPixelStoreParameters@ReadPixels"}) must fail the check

scripts/ci/retrace_verify_reason.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+# MobileGL - scripts/ci/retrace_verify_reason.py
+# Copyright (c) 2025-2026 MobileGL-Dev
+# Licensed under the GNU Lesser General Public License v3.0:
+#   https://www.gnu.org/licenses/gpl-3.0.txt
+#   https://www.gnu.org/licenses/lgpl-3.0.txt
+# SPDX-License-Identifier: LGPL-3.0-only
+# End of Source File Header
+
+"""Whether retrace-verify's corrupted-snapshot control went red for its own reason.
+
+The control replays OpenRA with MOBILEGL_PIPE_VERIFY_CORRUPT=GetRenderStateParameters and must go
+red with the comparator's divergence on that field: a red without it (another Fatal, a divergence
+on another field) proves nothing about the comparator. The check requires that divergence in the
+transcript; it does not rule out other failures beside it. run_trace_case.cmake prints the library
+log through message(STATUS), which never re-wraps, so each log line stays one transcript line.
+
+Usage: retrace_verify_reason.py TRANSCRIPT    (the control run's ctest -V output)
+Exit 0 when the divergence is there, 1 when it is not, 2 when the transcript cannot be read.
+"""
+import sys
+
+REASON = 'Fatal{PipeVerifyDiffer, "GetRenderStateParameters@'
+
+
+def carries_reason(text):
+    return REASON in text
+
+
+def main(argv=None):
+    argv = sys.argv[1:] if argv is None else argv
+    if len(argv) != 1:
+        print(__doc__)
+        return 2
+    try:
+        text = open(argv[0], encoding='utf-8', errors='replace').read()
+    except OSError as error:
+        print(f'::error::retrace_verify_reason: cannot read {argv[0]}: {error}')
+        return 2
+    if carries_reason(text):
+        print(f'retrace_verify_reason: the red carries {REASON}...')
+        return 0
+    print(f'::error::the corrupted-snapshot retrace went red without {REASON}...: '
+          'something other than the comparator failed it')
+    return 1
+
+
+if __name__ == '__main__':
+    sys.exit(main())