The auto-open useEffect in CodexConfigEditor and GeminiConfigEditor
created an inescapable loop: commonConfigError triggered modal open,
closing the modal didn't clear the error, so the effect immediately
reopened it — locking the entire UI.
- Remove auto-open useEffect from both Codex and Gemini config editors
- Convert common config modals to draft editing (edit locally, validate
before save) instead of persisting on every keystroke
- Add TOML/JSON pre-validation via parseCommonConfigSnippet before any
merge operation to prevent invalid content from being persisted
- Expose clearCommonConfigError so editors can clear stale errors on
modal close
