[v2] Dispatcher/ServerRunner receive-path swap — replaces BaseSession #2481

Job	Run time
checks / readme-snippets	11s
checks / pre-commit	32s
checks / test (3.11, locked, ubuntu-latest)	43s
checks / test (3.10, lowest-direct, ubuntu-latest)	50s
checks / test (3.10, lowest-direct, windows-latest)	1m 10s
checks / test (3.12, lowest-direct, windows-latest)	1m 25s
checks / test (3.11, lowest-direct, ubuntu-latest)	37s
checks / test (3.13, lowest-direct, ubuntu-latest)	54s
checks / test (3.12, lowest-direct, ubuntu-latest)	59s
checks / test (3.10, locked, windows-latest)	1m 12s
checks / test (3.11, locked, windows-latest)	1m 15s
checks / test (3.10, locked, ubuntu-latest)	52s
checks / test (3.14, locked, ubuntu-latest)	1m 49s
checks / test (3.14, lowest-direct, ubuntu-latest)	41s
checks / test (3.13, locked, ubuntu-latest)	45s
checks / test (3.13, locked, windows-latest)	1m 14s
checks / test (3.12, locked, ubuntu-latest)	55s
checks / test (3.11, lowest-direct, windows-latest)	1m 23s
checks / test (3.12, locked, windows-latest)	1m 22s
checks / test (3.13, lowest-direct, windows-latest)	1m 26s
checks / test (3.14, lowest-direct, windows-latest)	1m 22s
checks / test (3.14, locked, windows-latest)	2m 16s
all-green	5s
	23m 58s

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