Propagate contextvars.Context through anyio streams without modifying SessionMessage #1472

Job	Run time
checks / readme-snippets	14s
checks / pre-commit	37s
checks / test (3.10, locked, windows-latest)	2m 21s
checks / test (3.12, lowest-direct, windows-latest)	3m 57s
checks / test (3.10, lowest-direct, ubuntu-latest)	55s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 4s
checks / test (3.10, locked, ubuntu-latest)	56s
checks / test (3.12, locked, ubuntu-latest)	57s
checks / test (3.12, locked, windows-latest)	4m 3s
checks / test (3.11, lowest-direct, windows-latest)	2m 48s
checks / test (3.13, locked, ubuntu-latest)	48s
checks / test (3.11, locked, windows-latest)	3m 30s
checks / test (3.10, lowest-direct, windows-latest)	2m 33s
checks / test (3.14, lowest-direct, windows-latest)	2m 26s
checks / test (3.13, locked, windows-latest)	2m 30s
checks / test (3.13, lowest-direct, windows-latest)	3m 19s
checks / test (3.13, lowest-direct, ubuntu-latest)	59s
checks / test (3.11, locked, ubuntu-latest)	53s
checks / test (3.11, lowest-direct, ubuntu-latest)	54s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 20s
checks / test (3.14, locked, ubuntu-latest)	2m 20s
checks / test (3.14, locked, windows-latest)	3m 35s
all-green	3s
	43m 2s

Provide feedback