Orca adds GitHub stacked PRs

Orca turns a notoriously fragile Git workflow into a visible, guarded release sequence.

• –Shows each PR’s position, dependencies, and base branch in one view
• –Blocks merges when drafts, conflicts, missing approvals, failed checks, or stale branches remain
• –Uses GitHub’s atomic merge behavior to reduce accidental partial-stack merges
• –Especially useful for AI-assisted development, where parallel agents produce more interdependent changes
• –Makes Orca’s GitHub integration a real coordination layer, not just a PR viewer