Wraps GET /v1/:owner/:repo/git/trees/:sha and /git/blobs/:sha,
which had no CLI coverage:
- repo +git-tree -s <sha|ref> [--recursive]: paged tree entries
- repo +blob -s <sha> [--decode]: blob object; --decode prints the
base64 content as plain text for piping
Production-verified on gitlink.org.cn (tree listing by ref, blob
fetched by SHA and decoded byte-for-byte). 2 unit tests, README
examples, bilingual i18n keys.
Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>