Create React Router PR

Create the pull request handoff for completed React Router work. Default to a draft PR targeting main unless the user explicitly asks for a ready PR or a different base branch.

Preconditions

• Inspect git status --short --branch and git branch --show-current.
• Do not include unrelated dirty files. If unrelated changes are present, leave them unstaged and mention them.
• If the worktree is detached, create a branch from the current HEAD before committing. Use the branch name requested by the user, an existing repository convention, or <author>/<semantic-name> when no stronger convention is available.
• If already on a suitable named branch, use it.
• Confirm appropriate automated coverage exists or was added. Do not list routine CI-covered checks in the PR body.
• If user-facing functionality is being updated, check that the appropriate package has a change file under packages/<package>/.changes/. This is not necessary for docs-only, GitHub Actions/workflow-only, or dependency-maintenance PRs unless the dependency change itself has user-facing impact.

Context