fix: auto-send notifications/cancelled on anyio task cancellation #1921

Job	Run time
checks / pre-commit	32s
checks / readme-snippets	13s
checks / test (3.11, lowest-direct, windows-latest)	2m 35s
checks / test (3.10, lowest-direct, windows-latest)	3m 3s
checks / test (3.10, locked, ubuntu-latest)	47s
checks / test (3.10, locked, windows-latest)	2m 25s
checks / test (3.12, lowest-direct, ubuntu-latest)	51s
checks / test (3.12, locked, windows-latest)	4m 0s
checks / test (3.12, locked, ubuntu-latest)	49s
checks / test (3.11, locked, windows-latest)	2m 46s
checks / test (3.10, lowest-direct, ubuntu-latest)	47s
checks / test (3.11, lowest-direct, ubuntu-latest)	45s
checks / test (3.12, lowest-direct, windows-latest)	3m 39s
checks / test (3.14, locked, ubuntu-latest)	2m 22s
checks / test (3.11, locked, ubuntu-latest)	44s
checks / test (3.13, lowest-direct, ubuntu-latest)	50s
checks / test (3.13, locked, windows-latest)	2m 36s
checks / test (3.13, lowest-direct, windows-latest)	2m 59s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 13s
checks / test (3.14, lowest-direct, windows-latest)	2m 48s
checks / test (3.14, locked, windows-latest)	3m 15s
checks / test (3.13, locked, ubuntu-latest)	48s
all-green	5s
	40m 52s

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