Fix local_archive strategy to use git root directory for archive

[adpeyre]

• Bug fix #…?
• New feature?
• BC breaks?
• Tests added?
• Docs added?

When using the local_archive deploy strategy, git archive was run from the current working directory, which may differ
from the git repository root. This caused the command to fail when Deployer is invoked from a subdirectory.

This fix resolves the issue by:

• Resolving the git repository root with git rev-parse --show-toplevel
• Running git archive explicitly from that root directory using -C
• Using the full path to the generated archive for both upload() and unlink()

This ensures the strategy works correctly regardless of the directory from which Deployer is invoked.