feat(ng-dev/pr): allow merging multiple PRs in batch

[atscott]

Updates ng-dev pr merge to accept multiple pull request numbers or URLs. PRs are validated upfront with target branches and caretaker notes displayed in an aggregated summary, followed by a single confirmation prompt. Merges are performed sequentially with conflict and failure isolation so that an error on a middle PR does not prevent remaining PRs from landing.

[gemini-code-assist]

Code Review

This pull request refactors the merge tool to support batch merging of multiple pull requests sequentially, updating the CLI to accept multiple PRs and introducing a multi-phase validation and execution process. The feedback highlights a critical bug where strategy.check is called before strategy.prepare, which will fail because the local branches are not yet set up. Additionally, non-401 GitHub API errors during the initial validation phase are not caught, which defeats the batch isolation design by aborting the entire process. Finally, calling the single merge method results in duplicate API requests due to redundant loading and validation of the pull request.

[gemini-code-assist]

Code Review

This pull request introduces batch merging capabilities to the merge tool, allowing multiple pull requests to be validated upfront and merged sequentially with a single confirmation prompt. Key changes include updating the CLI to accept multiple PRs, implementing a mergeMany method in MergeTool, and refactoring error handling and PR parsing to support batch operations. Feedback on the changes suggests capturing the original branch or revision outside of the merge loop to prevent capturing a temporary branch if a previous iteration fails to restore the repository state.