Safety: Blocked TX messages during gas override

Route `a4653a9be878a408/00000235--c0955ae825/5` shows blocked TX messages from safety code during gas override on stock openpilot.

The issue occurs when openpilot continues sending non-zero accel commands for 1-2 frames during gas override.
While these blocked frames typically don't cause vehicle faults, on Rivian they can fault the ACC system. This route demonstrates the issue exists in stock openpilot, contrary to assumptions that it's sunnypilot-specific as discussed [here](https://github.com/commaai/opendbc/pull/2451#issuecomment-3061241323)

Start by replaying route a4653a9be878a408/00000235--c0955ae825/5 and inspecting the safety-code handling of gas override and blocked transmission frames. Compare the behavior with the discussion in opendbc/pull/2451; done means gas override produces no unsafe non-zero acceleration frames and does not fault Rivian ACC.

Written by the indexing model from the issue text.