Close v1.1.0 milestone and cut tag

[PAMulligan]

Goal

The v1.1.0 milestone is at 100% complete but remains open, and no v1.1.0 git tag has been published. Close the milestone and cut the release tag so downstream work can be planned against v1.2.0.

Acceptance criteria

• Confirm every issue in the v1.1.0 milestone is closed
• Update CHANGELOG.md with the v1.1.0 entry
• Tag v1.1.0 on main and push the tag
• Create a GitHub Release referencing the changelog
• Close the v1.1.0 milestone in the GitHub UI

Milestone

v1.2.0