Lake/external tables (e.g. Paimon in StarRocks) return 'There is currently no snapshot' on data reads when no snapshot exists yet, while metadata reads (DESC/SHOW CREATE) still succeed. Opening such a table surfaced the raw server error because executeTabSql stores the failure as an 'Error' result and never reached the column fetch. Detect that error result and retry the preview with LIMIT 0, which returns the table structure (columns + empty grid). Skip the synthetic-row-id re-query on this path since it is another data read that would fail the same way.
Add a configurable option in Settings > Navigation to reuse an existing data
tab instead of creating a new one each time a table is clicked in the sidebar.
Previously the sidebar tree refresh was skipped entirely in EDIT mode because
the check was gated on activeTab.mode === 'data', which is never true when
the structure editor is open. Now we pass a commentChanged flag through the
event chain and only refresh the tree when the comment was modified.
Replace the dialog-based TableStructureEditorDialog with a tab-based
TableStructureEditor, making it consistent with query editors, data
viewers, and object browsers. Users can now switch between editing
table structure and running queries freely.
Table/data tabs were missing schema in createTab, so the toolbar
"new query" button couldn't inherit schema from the active tab.
Also add schema to NewQueryTarget so resolveNewQueryTarget
propagates it from both sidebar and active tab contexts.
jischeng