feat: support in-place scaffolding for create . command

[sachin-duhan]

resolves #2418

[github-actions]

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[steve8708]

Thanks for the contribution @sachin-duhan!

I walked through the in-place path and think we should tighten the safety boundary before merging:

• resolveScaffoldTarget() allows .git and other existing files, but both failure paths still call cleanupOnFailure(targetDir). For in-place scaffolding, targetDir is process.cwd(), so a scaffold error could recursively delete the current directory, including .git.
• The allowlisted files aren’t actually protected: copyDir() overwrites existing files, and renameGitignore() can replace an existing .gitignore.
• tryGitInit(targetDir) will also initialize, stage, and commit when .git already existed, which could create an unexpected commit in the user’s repository.

I’d suggest staging into a temporary directory, copying only new files into the current directory after success, and cleaning up only the staging directory on failure. We should also detect pre-existing Git metadata and skip init/commit in that case.

Could we add tests covering preservation of .git, README.md, and .gitignore, unchanged Git history, and cleanup after an injected scaffold failure?