Propagate contextvars.Context through anyio streams without modifying SessionMessage #1469

Job	Run time
checks / readme-snippets	10s
checks / pre-commit	36s
checks / test (3.11, lowest-direct, windows-latest)	3m 14s
checks / test (3.10, lowest-direct, windows-latest)	2m 36s
checks / test (3.10, locked, ubuntu-latest)	52s
checks / test (3.12, locked, windows-latest)	3m 47s
checks / test (3.11, locked, ubuntu-latest)	53s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 0s
checks / test (3.12, lowest-direct, windows-latest)	3m 54s
checks / test (3.11, locked, windows-latest)	2m 29s
checks / test (3.12, locked, ubuntu-latest)	56s
checks / test (3.10, lowest-direct, ubuntu-latest)	52s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 26s
checks / test (3.10, locked, windows-latest)	2m 28s
checks / test (3.11, lowest-direct, ubuntu-latest)	52s
checks / test (3.13, locked, ubuntu-latest)	49s
checks / test (3.13, lowest-direct, ubuntu-latest)	54s
checks / test (3.13, locked, windows-latest)	2m 21s
checks / test (3.14, lowest-direct, windows-latest)	2m 42s
checks / test (3.13, lowest-direct, windows-latest)	2m 42s
checks / test (3.14, locked, windows-latest)	3m 14s
checks / test (3.14, locked, ubuntu-latest)	2m 20s
all-green	4s
	41m 11s

Provide feedback