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Fix Python 3.8/3.9 jobs on Ubuntu 26.04, pin actions, and add zizmor #3097

Job	Run time
install/import (ubuntu-latest, 3.10)	10s
test (macos, 3.13)	11m 12s
install/import (ubuntu-24.04, 3.9)	15s
install/import (ubuntu-24.04, 3.8)	19s
install/import (macos-latest, 3.9)	32s
install/import (macos-latest, 3.8)	1m 5s
install/import (macos-latest, 3.10)	34s
install/import (windows-latest, 3.9)	1m 3s
install/import (windows-latest, 3.10)	1m 12s
test (windows, 3.15t)	42m 42s
test (ubuntu, 3.14t)	4m 51s
install/import (windows-latest, 3.8)	1m 17s
test (ubuntu, 3.14)	3m 45s
test (windows, 3.11)	47m 1s
test (ubuntu, 3.12)	4m 19s
test (ubuntu, 3.11)	4m 2s
test (ubuntu, 3.15)	4m 7s
test (windows, 3.12)	47m 34s
test (macos, 3.12)	12m 24s
test (windows, 3.14)	44m 52s
test (windows, 3.12, gix)	38m 35s
test (macos, 3.14)	12m 25s
test (ubuntu, 3.13)	6m 1s
test (macos, 3.15)	12m 13s
test (ubuntu, 3.12, gix)	5m 8s
test (macos, 3.11)	17m 1s
test (windows, 3.15)	33m 34s
test (windows, 3.14t)	35m 8s
test (ubuntu, 3.15t)	5m 7s
test (macos, 3.12, gix)	7m 49s
test (windows, 3.13)	48m 32s
	7h 34m 49s