lint

CI: update Go (1.26); mark several tests flaky #2357

Job	Run time
other / yaml \| shell	6s
project checks / commits, licenses...	1m 23s
go / darwin	2m 23s
go / freebsd	2m 29s
build for / go 1.26	7m 34s
build for / go canary	4s
build for / go 1.25	1m 2s
go / linux (go canary)	7s
go / linux	2m 29s
go / windows	2m 30s
	20m 7s

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