fix: avoid positional substitution in clean_gone

[yudin-s]

Summary

• Replace awk '{print $1}' snippets in /clean_gone with sed field extraction
• Avoid Claude Code command positional substitution stripping literal $1 and breaking branch/worktree parsing

Fixes #52226.

Test plan

• rg -n "awk '\{print $1\}'|$1" plugins/commit-commands/commands/clean_gone.md
• git diff --check