Maintenance roadmap: modern Python, CI, and releases

[waddell]

UDST is resuming active maintenance of Orca.

Initial priorities:

• Restore CI on supported Python versions
• Remove Python 2 compatibility
• Modernize packaging metadata
• Establish main as the single integration branch
• Configure required CI and review protections
• Prepare and publish a maintenance release
• Document the supported Python and dependency policy
• Add automated release publishing

PR #62 begins the CI and compatibility work.

This issue will remain open until the maintenance and release process is operational.