Replace setTimeout-based editingKey activation with a useEffect that
watches propertyEntries. When the newly added property appears in
propertyEntries (after the async backend write completes), the effect
sets editingKey, ensuring the editor/picker opens regardless of timing.
The old setTimeout(fn, 0) approach raced with the async frontmatter
write — editingKey was set before the property existed in the DOM,
so the editing state had no matching PropertyRow to activate.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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