fix(guard): scope destructive Git cleanup to Path-owned targets

[cristianuibar]

Forced Git cleanup commands were blocked even when the target belonged to the project rather than GSD Path. The guard now permits resolvable ordinary local branch/ref deletions and force-removal of registered unmanaged worktrees, while protecting GSD Path namespace refs, the STATE-bound branch, recorded task branches, managed worktrees, and unknown or unresolved targets.

The guard resolves literal targets in the repository selected by per-segment cd and stacked git -C options. Ambiguous shell or environment contexts fail closed. Remote-tracking branch deletion remains conservatively denied.

Verification:

• 121 tests passed in 3.706s: python3 -B -m unittest tests.test_guard_hook
• git diff --check passed
• Python compilation check passed
• Skill-resource sync passed: 490 resources, 0 warnings, no extra changes
• Independent Sol review found no material defects

Worktree: /home/cristian/orca/workspaces/gsd-path/guard-blocks-forced-branch-delete-and-worktree-f

Fixes #344