feat(frontend): suggested-first ordering + filter box in the schema-linking columns modal

Wide tables (e.g. 116 columns, 3 suggested) made curation a scroll hunt. Now the
modal lists suggested columns first (stable sort on the descriptor flag, so
toggling never reorders rows) and adds a filter box matching name + description,
with a "shown/total" count. Selection stays keyed by column name, so the response
column order is unchanged (catalog order). Applies to read-only (excluded) tables too.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/widgets/SchemaColumnsDialog.test.tsx

@@ -46,3 +46,62 @@ test("readOnly renders no checkboxes and no bold", () => {
   expect(screen.getByText("cod_paz")).toBeInTheDocument();
   expect(screen.getByText("cod_paz").className).not.toContain("font-bold");
 });
+
+const wide: SchemaTable = {
+  id: "t",
+  name: "t",
+  kind: "promote",
+  columns: [
+    { name: "aaa", description: "alfa", suggested: false },
+    { name: "zzz_key", description: "chiave", suggested: true },
+    { name: "bbb", description: "Codice beta", suggested: false },
+  ],
+};
+
+test("suggested columns are listed first, then catalog order (stable)", () => {
+  render(
+    <SchemaColumnsDialog
+      table={wide}
+      open
+      readOnly={false}
+      selected={new Set()}
+      onToggle={() => {}}
+      onClose={() => {}}
+    />
+  );
+  const order = screen.getAllByRole("checkbox").map((cb) => cb.getAttribute("aria-label"));
+  expect(order).toEqual(["zzz_key", "aaa", "bbb"]);
+});
+
+test("filter narrows visible columns by name", async () => {
+  render(
+    <SchemaColumnsDialog
+      table={wide}
+      open
+      readOnly={false}
+      selected={new Set()}
+      onToggle={() => {}}
+      onClose={() => {}}
+    />
+  );
+  await userEvent.type(screen.getByRole("textbox", { name: /filter/i }), "zzz");
+  const order = screen.getAllByRole("checkbox").map((cb) => cb.getAttribute("aria-label"));
+  expect(order).toEqual(["zzz_key"]);
+  expect(screen.queryByText("aaa")).toBeNull();
+});
+
+test("filter matches the description too", async () => {
+  render(
+    <SchemaColumnsDialog
+      table={wide}
+      open
+      readOnly={false}
+      selected={new Set()}
+      onToggle={() => {}}
+      onClose={() => {}}
+    />
+  );
+  await userEvent.type(screen.getByRole("textbox", { name: /filter/i }), "codice");
+  const order = screen.getAllByRole("checkbox").map((cb) => cb.getAttribute("aria-label"));
+  expect(order).toEqual(["bbb"]);
+});