fix ContextVar persistence across cells (#1462) #3696

Job	Run time
Test Lint	1m 2s
Make SDist	29s
Test Prereleases	2m 30s
link_check	3m 40s
test_docs	44s
Test Minimum Versions	3m 1s
test_without_debugpy (ubuntu-latest, 3.10)	2m 30s
build (ubuntu-latest, qt6, 3.13)	2m 46s
check_release	1m 45s
build (ubuntu-latest, qt5, 3.14)	2m 49s
build (windows-latest, qt5, pypy-3.11)	8m 21s
build (macos-latest, qt5, 3.14)	2m 50s
build (windows-latest, qt6, 3.12)	3m 57s
build (windows-latest, qt6, pypy-3.11)	7m 24s
build (windows-latest, qt5, 3.14)	5m 17s
build (windows-latest, qt6, 3.10)	3m 36s
build (ubuntu-latest, qt6, 3.12)	2m 48s
build (macos-latest, qt6, 3.10)	3m 12s
build (macos-latest, qt5, 3.10)	2m 36s
build (ubuntu-latest, qt6, pypy-3.11)	3m 51s
build (macos-latest, qt5, pypy-3.11)	5m 22s
build (ubuntu-latest, qt6, 3.10)	2m 52s
build (macos-latest, qt6, 3.11)	3m 5s
build (ubuntu-latest, qt5, 3.10)	2m 44s
build (windows-latest, qt6, 3.11)	4m 15s
build (macos-latest, qt6, 3.12)	2m 46s
build (windows-latest, qt5, 3.10)	4m 45s
build (ubuntu-latest, qt6, 3.11)	2m 42s
build (macos-latest, qt6, 3.13)	2m 36s
build (macos-latest, qt6, pypy-3.11)	4m 15s
build (windows-latest, qt6, 3.13)	3m 50s
build (ubuntu-latest, qt5, pypy-3.11)	4m 31s
Install from SDist and Test	2m 31s
coverage	9s
	1h 51m 31s

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