fix: handle git-lfs pointer files

[YogliB]

Summary

What

Handle git-lfs pointer files in tarball clones by extracting to a temp directory, detecting exact pointer files, and falling back to git clone when needed.

Why

Some repositories serve tarballs that contain Git LFS pointer files instead of real blob contents, so tarball-first cloning needs a fallback path for those repos.

resolved: #381

Changes

• Extract tarballs into a temporary directory before copying files into the destination.
• Detect exact Git LFS pointer files, including the canonical and legacy Hawser pointer versions.
• Fall back to git clone only when a real pointer file is present.
• Keep the downloaded tarball cached and keep the warning when fallback happens.
• Add regression tests for quoted pointer text, canonical pointers, and legacy pointers.

Testing

How you verified this (commands, scenarios, or N/A):

• Automated tests (bun run test)
• Manual / CLI check if user-facing behavior changed
• CI passes

Review notes

Breaking changes (or none)

None.

Risks / rollout (or none)

The tarball path now scans extracted files before copying them into place.

Focus areas for reviewers (optional)

Tar extraction flow, pointer detection, and the regression coverage for pointer detection and fallback.

Checklist

• Error paths and exit codes considered where relevant
• Help text, completions, or docs updated if user-facing strings changed
• Squashed to a single commit
• No unrelated drive-by changes