feat: add --get-url flag to git ls-remote for URL config overrides

[unicoderbot]

Summary

Adds the --get-url flag to the git ls-remote command in the Git.reachable() method to respect git config URL rewrites (such as url.<base>.insteadOf).

Why

When checking if a git remote is reachable, the CLI was not respecting git config URL overrides like insteadOf. This caused the reachability check to fail for URLs that had been configured with rewrites, while the actual flutter pub get command would succeed because it honors these overrides.

By passing --get-url to git ls-remote, the check now behaves consistently with how the actual dependency pull resolves remotes.

Changes

• Added --get-url flag to git ls-remote command in Git.reachable()
• Updated method documentation to explain the flag's purpose
• Added test case to verify the flag is passed correctly

Closes #1097