chore(base): drop pre-virtualizer-fix scroll-jump workarounds

Two pieces of code added under the wrong height-mismatch theory of
the inline-embed scroll jump are no longer load-bearing now that the
real cause (virtual-core's _willUpdate calling _scrollToOffset(NaN))
is fixed by the initialOffset seed in grid-container.tsx:

  - BaseTableSkeleton's `rows` prop, whose only consumer was the
    "creating database" placeholder passing rows=0 to "match" the
    eventual empty-base height. Reverted to a fixed 10-row skeleton.
  - The Database slash command's React Query cache prefill of
    ["bases", id] and ["base-rows", id, …] (~30 lines), which
    existed to skip BaseTable's own loading skeleton on swap. The
    create endpoint return type is back to { id }.

The placeholder approach (pendingKey + setNodeMarkup patch) stays —
that's what gives the user visible state during the create request,
unrelated to the scroll jump.

apps/client/src/features/base/components/base-table-skeleton.tsx

@@ -5,24 +5,14 @@ import classes from "@/features/base/styles/base-table-skeleton.module.css";
 const ROW_NUMBER_WIDTH = 64;
 const COLUMN_WIDTH = 180;
 const COLUMN_COUNT = 6;
-const DEFAULT_ROW_COUNT = 10;
+const ROW_COUNT = 10;
 
 // Deterministic per-cell widths so the skeleton doesn't flicker between
 // renders. Values are rough normal distribution around 55-85 % of cell.
 const CELL_WIDTH_RATIOS = [0.78, 0.62, 0.84, 0.55, 0.71, 0.66];
 const HEADER_WIDTH_RATIOS = [0.42, 0.58, 0.5, 0.64, 0.46, 0.54];
 
-type BaseTableSkeletonProps = {
-  // Override the body row count. Pass 0 when rendering as the
-  // "creating database" placeholder for a freshly-inserted inline embed
-  // — the eventual empty base has no rows, so a 10-row skeleton would
-  // shrink ~330px on swap and trip the browser's scrollY clamp.
-  rows?: number;
-};
-
-export function BaseTableSkeleton({
-  rows = DEFAULT_ROW_COUNT,
-}: BaseTableSkeletonProps = {}) {
+export function BaseTableSkeleton() {
   const gridTemplateColumns = [
     `${ROW_NUMBER_WIDTH}px`,
     ...Array.from({ length: COLUMN_COUNT }, () => `${COLUMN_WIDTH}px`),
@@ -64,7 +54,7 @@ export function BaseTableSkeleton({
             </div>
           ))}
 
-          {Array.from({ length: rows }).map((_, rowIndex) => (
+          {Array.from({ length: ROW_COUNT }).map((_, rowIndex) => (
             <div key={`row-${rowIndex}`} style={{ display: "contents" }}>
               <div className={gridClasses.cell}>
                 <div className={classes.cellInner}>