Extend worktree creation, remote-conflict detection, and the Checks panel UI to support linked PRs from Bitbucket, Azure DevOps, and Gitea alongside GitHub and GitLab.
* Extract shared metadata lookup helpers to map provider-specific review identifiers.
* Update remote-conflict validation to check hosted reviews on target providers during worktree creation.
* Propagate provider-specific PR states through the RPC layers and into the Checks and Source Control UI panels.