Fix unknown-method error code and add a protocol version registry (#2… #2620

Job	Run time
checks / pre-commit	31s
checks / test (3.14, lowest-direct, ubuntu-latest)	50s
checks / readme-snippets	16s
checks / test (3.13, locked, windows-latest)	1m 9s
checks / test (3.11, locked, windows-latest)	1m 31s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 0s
checks / test (3.12, locked, ubuntu-latest)	52s
checks / test (3.11, locked, ubuntu-latest)	51s
checks / test (3.13, lowest-direct, windows-latest)	1m 38s
checks / test (3.13, locked, ubuntu-latest)	49s
checks / test (3.11, lowest-direct, windows-latest)	1m 30s
checks / test (3.10, lowest-direct, windows-latest)	1m 20s
checks / test (3.14, locked, windows-latest)	3m 26s
checks / test (3.12, lowest-direct, windows-latest)	1m 38s
checks / test (3.10, locked, ubuntu-latest)	49s
checks / test (3.11, lowest-direct, ubuntu-latest)	57s
checks / test (3.14, locked, ubuntu-latest)	1m 59s
checks / test (3.12, locked, windows-latest)	5m 39s
checks / test (3.10, lowest-direct, ubuntu-latest)	57s
checks / test (3.14, lowest-direct, windows-latest)	1m 44s
checks / test (3.12, lowest-direct, ubuntu-latest)	59s
checks / test (3.10, locked, windows-latest)	2m 1s
all-green	4s
	32m 30s

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