Serve the 2026-07-28 protocol over stdio: decide the era from the opening message #3594

Job	Run time
checks / pre-commit	50s
checks / readme-snippets	15s
checks / test (3.10, locked, windows-latest)	1m 53s
checks / test (3.11, lowest-direct, windows-latest)	1m 53s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 10s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 32s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 26s
checks / docs	1m 3s
checks / test (3.10, locked, ubuntu-latest)	1m 34s
checks / test (3.13, locked, windows-latest)	1m 47s
checks / test (3.11, locked, windows-latest)	1m 49s
checks / test (3.11, locked, ubuntu-latest)	1m 6s
checks / test (3.13, locked, ubuntu-latest)	1m 16s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 22s
checks / test (3.10, lowest-direct, windows-latest)	1m 45s
checks / test (3.12, locked, ubuntu-latest)	1m 39s
checks / test (3.12, lowest-direct, windows-latest)	2m 0s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 24s
checks / test (3.13, lowest-direct, windows-latest)	1m 54s
checks / test (3.14, lowest-direct, windows-latest)	1m 47s
checks / test (3.14, locked, ubuntu-latest)	1m 25s
checks / test (3.14, locked, windows-latest)	2m 14s
checks / test (3.12, locked, windows-latest)	1m 47s
all-green	4s
	34m 55s

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