Prevent metadata generation from waiting on stdin

[JMastro-OneMIT]

Summary

• drop the extra quoting around the extension UUID so cleanup no longer errors when archives are missing
• append the git shortlog output directly into metadata.js so the generated file is properly populated
• force the clean target to ignore missing archives, keeping make dev from emitting spurious errors
• guard metadata generation's git shortlog invocation so it runs without waiting on stdin

Testing

• npm test (fails: prettier --list-different "./**/*.{js,jsx,ts,tsx,json}" flags lib/prefs/metadata.js that predates this change)

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https://chatgpt.com/codex/tasks/task_e_68d039c51b08832d808ea093fe0bd9f4