feat: Add reusable SQL query blocks and artifact tabs - #669

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@apps/sqlrooms-cli-ui/src/context/createArtifactContextAiTools.ts`:
- Around line 104-125: The sql-query branch reads state.sqlEditor.config.queries
and queryResultsById without guaranteeing the artifact-backed query is loaded,
so add a guard to ensure the backing query is initialized before reading
context: if query is undefined, call a new or existing initializer (e.g.,
ensureQueryLoadedForArtifact(artifactId) or dispatch/selectQuery for artifactId)
to load/create the query into state.sqlEditor.config.queries and
queryResultsById, then re-read query and result; finally return the payload
using the now-guaranteed query and result. Ensure you reference artifactId,
state.sqlEditor.config.queries, and state.sqlEditor.queryResultsById in the
change.

In `@packages/data-table/src/DataTablePaginated.tsx`:
- Around line 173-175: The Tailwind v3 important modifier syntax is used in
DataTablePaginated.tsx; update the className usages on TableHeader and TableRow
to use Tailwind v4 placement of the "!" at the end of the utility (e.g., replace
"[&_tr]:!border-b-0" with "[&_tr]:border-b-0!" and any "!border-b-0" occurrences
with "border-b-0!") so the TableHeader and TableRow className strings conform to
Tailwind v4.

In `@packages/sql-editor/src/components/QueryEditorPanelEditor.tsx`:
- Around line 51-58: The current editorOptions memo unconditionally spreads
CODEMIRROR_OPTIONS then sets lineNumbers, foldGutter, and highlightActiveLine to
false or undefined, which overwrites defaults when compact is false; change it
so overrides are only applied when compact is true (e.g., conditionally include
properties) so CODEMIRROR_OPTIONS values remain intact when compact is false;
update the useMemo that defines editorOptions (referencing editorOptions,
CODEMIRROR_OPTIONS, and compact) to only inject the false overrides in compact
mode.

In `@packages/sql-editor/src/SqlEditorSlice.tsx`:
- Around line 327-336: The current removeQuery() implementation recreates a
synthetic 'default' query when the last query is deleted; change removeQuery()
to perform a pure deletion (remove the id-addressable state from config.queries,
config.openTabs, config.selectedQueryId without injecting a 'default' entry) so
it can be used by artifact/block deletion paths without leaving phantom tabs,
and move the "always keep one workbench tab" fallback into the UI/tab-specific
delete flow (the function that handles user tab deletions—e.g., the
deleteTab/removeActiveTab handler) so the editor UI ensures at least one visible
tab while library-level removeQuery() remains generic and composable.