Ensure all messages used in safety have checksums and counters

## TODO

| Safety mode | RX messages missing counters | RX messages missing checksums | PRs to address |
|---|---:|---:|---|
| [Chrysler](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/chrysler.h) | 1 | 1 | TBD |
| [Ford](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/ford.h) | 4 | 4 | TBD |
| [GM](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/gm.h) | 7 | 7 | TBD |
| [Hyundai](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/hyundai.h) | 5* | 5* | TBD |
| [Mazda](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/mazda.h) | 5 | 5 | TBD |
| [MG](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/mg.h) | 1 | 1 | TBD |
| [Nissan](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/nissan.h) | 5 | 5 | TBD |
| [PSA](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/psa.h) | 4 | 4 | TBD |
| [Subaru](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/subaru.h) | 5 | 5 | TBD |
| [Toyota](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/toyota.h) | 7 | 4 | TBD |
| [Volkswagen MQB](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/volkswagen_mqb.h) | 2 | 2 | TBD |
| [Volkswagen PQ](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/volkswagen_pq.h) | 4 | 3 | TBD |

## DONE

| Safety mode | RX messages missing counters | RX messages missing checksums | PRs to address |
|---|---:|---:|---|
| [Body](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/body.h) | 0 | 0 | [PR #3777](https://github.com/commaai/opendbc/pull/3777) |
| [Honda](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/honda.h) | 0 | 0 | — |
| [Rivian](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/rivian.h) | 0 | 0 | [PR #3776](https://github.com/commaai/opendbc/pull/3776) |
| [Tesla](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/tesla.h) | 0 | 0 | — |
| [Volkswagen MLB](https://github.com/commaai/opendbc/blob/master/opendbc/safety/modes/volkswagen_mlb.h) | 0 | 0 | — |

Counts fold alternate bus/length definitions into one logical RX message. `*` Hyundai includes the legacy-only `0x386` and `0x394` cases; newer Hyundai configurations already check those counters/checksums.

Read the safety mode headers linked in the TODO table, starting with one remaining mode, and compare them with the completed modes and PRs #3776 and #3777. Track the affected RX messages and their counter/checksum status; the work is done when the TODO counts reach zero and each addressed mode has a corresponding PR or completed change.

Written by the indexing model from the issue text.