fix(web): focus-visible rings on remaining controls + live search count (#69)

Keyboard focus was invisible on the objects-table sort headers and
page-size select, breadcrumb links, the external-URI link, and the
combobox input/clear/trigger. Apply the shared focusRing helper in app
code and the kit's inline focus-visible classes (matching input.tsx)
in ui/combobox.

Make the search result count a role="status" live region so screen
readers announce updated counts while typing; the existing search test
now asserts the count through getByRole("status").

Closes #69

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

web/src/search/search.test.tsx

@@ -60,7 +60,8 @@ test("typing searches and renders highlighted rich rows", async () => {
   expect(await screen.findByText("Bronze figurine")).toBeInTheDocument();
   const mark = await screen.findByText("bronze");
   expect(mark.tagName).toBe("MARK");
-  expect(screen.getByText(/~\s*25 results/i)).toBeInTheDocument();
+  // The estimated count lives in a status region so updates are announced.
+  expect(screen.getByRole("status")).toHaveTextContent(/~\s*25 results/i);
   expect(screen.getByText(/1962-04-03/)).toBeInTheDocument();
 });