Misc file system fixes, especially for windows#15301

Merged

Ericson2314 merged 7 commits intoNixOS:masterfrom

obsidiansystems:file-system-prep

Feb 20, 2026

Commits on Feb 20, 2026

`openFileEnsureBeneathNoSymlinks` now returns `AutoCloseFD`
Ericson2314
committed
libutil: refactor `AutoCloseFD::fsync` into standalone `syncDescriptor`
amaanq
committed
Change `writeFile(AutoCloseFD &, ...)` to take a `Descriptor`
Ericson2314
committed