fix: skip worktree listing in pure prune mode

[rokuosan]

Overview

Make git wtclean --prune (without a delete option) only clean stale worktree metadata, instead of also listing active worktrees.

Previously, pure prune mode ran git worktree list and printed Would remove: <path> for every active worktree before pruning. Those entries were never actually removed, so the dry-run-style output was misleading next to the real git worktree prune action.

Changes

• internal/wtclean/app.go
  • Skip listing active worktrees when --prune is used without -d/-D; only git worktree prune runs in that case.
  • Drop the unused found count from the prune summary (Done. prune_checked=… failed=…).
• README.md
  • Document that --prune by itself does not inspect or remove active linked worktrees.

Notes

• Other modes are unchanged: bare dry run, -d/-D, and -d --prune still list (and remove) worktrees as before.

Validation

• go test ./...