test: canary to prove 5.1 smoke goes red

Temporary SystemExit(1) in bmesh-gear so the labeled 5.1 job is observed failing. Reverted in the next commit.

Signed-off-by: TMHSDigital <154358121+TMHSDigital@users.noreply.github.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: TMHSDigital

examples/bmesh-gear/bmesh_gear.py

@@ -194,6 +194,7 @@ def main():
     p.add_argument("--engine", default="eevee", choices=("eevee", "cycles"),
                    help="render engine for --output (cycles for GPU-less hosts)")
     args = p.parse_args(argv)
+    raise SystemExit(1)  # phase-4 canary: prove 5.1 smoke fails
 
     obj = build_gear()
     code = check(obj)