Tip of feature/imu_factor_with_gravity before the 2026-08-01 rebase

Bump version

Bump version

Merge branch 'develop' into release/4.2a5

Merge pull request borglab#1073 from borglab/release/4.2a4

Finish 4.2a3

Fix single quotes

Finish 4.2a1

Finish 4.2a0

Before API-breaking change in discrete