fix(worktree): refuse dirty terminal finalization

[chubes4]

Closes #935

Summary

• reject terminal and cleanup-signalling lifecycle updates when porcelain status is dirty
• report bounded staged, unstaged, and untracked path evidence with remediation
• preserve active lifecycle updates and avoid mutating metadata on failed finalization
• reuse the cleanup git-status probe contract

How to test

1. Run php tests/worktree-add-lifecycle.php.
2. Run git diff --check origin/main...HEAD.

Compatibility

Only terminal or cleanup-signalling lifecycle transitions change behavior. Dirty active worktrees remain valid; callers must commit, stash, or discard changes before marking a worktree terminal.