fix(worktree): stale dir cleanup, random adjectives, and close hook fixes

[neumie]

Summary

• Fix worktree creation failing with "already exists" when a stale directory is left from a previous removal
• Randomize adjective order in branch name generation so Phase 2 names don't always start with "velk"
• Fix worktree close silently doing nothing when the before_remove hook terminal fails to spawn — now shows an error and aborts
• Fix on_worktree_close hook running with a deleted CWD

Changes

Stale worktree directory cleanup (repository.rs)

• Add clean_stale_worktree_dir() that checks git worktree list --porcelain to distinguish active worktrees from stale directories
• Removes stale dirs and prunes metadata before git worktree add
• Called from both create_worktree and create_worktree_with_start_point

Random adjective order (branch_names.rs)

• Shuffle ADJECTIVE_STEMS indices alongside goods indices
• Phase 2 and Phase 3 now pick a random adjective instead of always starting with "velk"

Close worktree hook fixes (close_worktree_dialog.rs, actions/project.rs)

• When fire_before_worktree_remove_async returns empty results (hook terminal failed to create), show error and abort instead of silently closing the dialog with no removal
• Move fire_on_worktree_close before git worktree remove in remove_worktree_project so the hook runs with a valid CWD

Test plan

• Manually leave a stale directory at the expected worktree path, then create a worktree — should succeed
• Create enough worktrees to exhaust plain names — adjective+good combos should use varied adjectives
• Configure a before_remove hook, close a worktree — hook should complete before removal
• Kill the shell before closing a worktree with before_remove hook — should show error, not silently skip
• Configure an on_close hook, close a worktree — hook should run with valid CWD