Make client-side cancellation work over the 2026 transports #3357

Job	Run time
checks / readme-snippets	12s
checks / docs	43s
checks / pre-commit	54s
checks / test (3.10, locked, ubuntu-latest)	1m 32s
checks / test (3.11, lowest-direct, windows-latest)	1m 49s
checks / test (3.12, locked, ubuntu-latest)	1m 41s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 21s
checks / test (3.12, lowest-direct, windows-latest)	2m 8s
checks / test (3.11, locked, windows-latest)	1m 58s
checks / test (3.10, locked, windows-latest)	2m 48s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 31s
checks / test (3.10, lowest-direct, windows-latest)	2m 29s
checks / test (3.13, locked, windows-latest)	1m 55s
checks / test (3.13, locked, ubuntu-latest)	1m 23s
checks / test (3.12, locked, windows-latest)	2m 21s
checks / test (3.11, locked, ubuntu-latest)	1m 22s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 21s
checks / test (3.14, lowest-direct, windows-latest)	1m 42s
checks / test (3.13, lowest-direct, windows-latest)	1m 52s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 33s
checks / test (3.14, locked, ubuntu-latest)	2m 19s
checks / test (3.14, locked, windows-latest)	2m 39s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 8s
all-green	5s
	38m 46s

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