chore: bump to nightly-2026-02-21 with mathlib at nightly-testing-202…

…6-02-21

manual bump to nightly-2026-02-17

chore(CombinatoryLogic): miscellaneous grind golfing (#345)

Low priority

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Co-authored-by: twwar <[email protected]>
Co-authored-by: Chris Henson <[email protected]>

chore: bump toolchain to v4.28.0 (#339)

chore: bump to nightly-2026-02-16 with mathlib at nightly-testing-202…

…6-02-16

chore: bump to nightly-2026-02-15-rev1 with mathlib at nightly-testin…

…g-2026-02-15-rev1

chore: bump to nightly-2026-02-13-rev2 with mathlib at nightly-testin…

…g-2026-02-13-rev2

chore: bump to nightly-2026-02-10 with mathlib at nightly-testing-202…

…6-02-10

simp +instances in CslibTests

Merge main into nightly-testing