Enforce configured host Git identities

[chubes4]

Summary

• add generic host-scoped Git identity policy resolution
• enforce exact configured name and email before commits and internal squash/rebase pushes
• write configured identities to worktree-local Git config during managed worktree creation
• preserve normal ambient Git identity behavior for unconfigured hosts

Compatibility

Unconfigured hosts retain existing Git behavior. Integrations opt into enforcement through the generic policy filter.

How to test

1. Run php tests/workspace-git-identity-policy.php.
2. Run php -l inc/Workspace/WorkspaceGitIdentityPolicy.php.
3. Run composer validate --no-check-publish.

Closes #933