Feature request: Add --force flag to `clean --merged` to remove worktrees with uncommitted changes

[maro114510]

Feature Request

Summary

Add a --force / -f flag to git gtr clean (specifically for --merged) that bypasses the dirty-worktree safety check. This allows removing worktrees even when they contain uncommitted changes or untracked files.

Current Behavior

Currently, clean --merged skips any worktree that has uncommitted changes or untracked files to prevent accidental data loss.
(Reference: _clean_should_skip in lib/commands/clean.sh)

While this is a sensible default, it can be tedious when you know the changes are disposable (e.g., build artifacts or experimental logs) and the branch is already safely merged.

Proposed Change

Add -f / --force to the clean command. When this flag is provided:

• The uncommitted changes check is skipped.
• The untracked files check is skipped.

Note on Safety:

• This flag only bypasses the "dirty" check.
• It does not imply --yes. Users will still be prompted for confirmation unless --yes is also provided.
• Detached HEAD worktrees and the current active worktree should still be protected/skipped.

Usage

# Force remove merged worktrees even if dirty
git gtr clean --merged --force

# Combined with auto-confirm
git gtr clean --merged -f --yes

I'm happy to contribute and open a PR if the approach looks good to you. Thanks!