fix(create): scaffold libraries in git directories

[RSS1102]

Summary

• allow the built-in vite:library template to scaffold into a target containing only .git by passing --force to degit
• re-check target availability immediately before degit so existing user files are not overwritten
• surface captured degit output and fail when the command does not produce package.json
• cover .git directories, worktree .git files, user-file preservation, and degit failure propagation

Testing

• vp check
• pnpm -F vite-plus test src/create/__tests__ (13 files, 185 tests)
• cargo test -p vite_cli_snapshots -- create_library_in_git_directory (record and compare modes)
• manual end-to-end vp create vite:library --directory . in a freshly initialized Git repository

Fixes #2254

[netlify]

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[fengmk2]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Hooray!

Reviewed commit: 8b25b757f7

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[fengmk2]

@RSS1102 Thanks!