Canonicalize short aliases before git passthrough

[sedge-bot]

Summary

• map short aliases b/s/d/l to branch/status/diff/log before invoking git passthrough
• add conformance coverage for alias passthrough cases like l --graph and d --name-only
• preserve the existing passthrough behavior for other git args while fixing the short-alias mismatch

Validation

• conformance coverage updated locally for the alias passthrough cases

Notes

• full zig build validation is still blocked in this environment because libgit2 install resolution is not working on this host