fix(frontend): make NavSessions rows keyboard-accessible (role/tabIndex/Enter+Space)

frontend/src/shell/NavSessions.test.tsx

@@ -25,3 +25,12 @@ test("active session is highlighted", () => {
   render(<NavSessions sessions={SESSIONS} activeSessionId="s2" onOpenPanel={vi.fn()} menuFor={() => null} />);
   expect(screen.getByTestId("session-item-s2")).toHaveAttribute("data-active", "true");
 });
+
+test("pressing Enter on a focused row opens the panel", async () => {
+  const onOpenPanel = vi.fn();
+  render(<NavSessions sessions={SESSIONS} activeSessionId={null} onOpenPanel={onOpenPanel} menuFor={() => null} />);
+  const row = screen.getByTestId("session-item-s1");
+  row.focus();
+  await userEvent.keyboard("{Enter}");
+  expect(onOpenPanel).toHaveBeenCalledWith("s1");
+});

frontend/src/shell/NavSessions.tsx

@@ -27,8 +27,17 @@ export function NavSessions({ sessions, activeSessionId, onOpenPanel, menuFor }:
               data-testid={`session-item-${s.id}`}
               data-active={active ? "true" : "false"}
               onClick={() => onOpenPanel(s.id)}
+              role="button"
+              tabIndex={0}
+              aria-label={s.name || s.question || s.id}
+              onKeyDown={(e) => {
+                if (e.key === "Enter" || e.key === " ") {
+                  e.preventDefault();
+                  onOpenPanel(s.id);
+                }
+              }}
               className={[
-                "group flex w-full cursor-pointer items-start gap-1 rounded-lg px-2.5 py-2 text-left transition-colors",
+                "group flex w-full cursor-pointer items-start gap-1 rounded-lg px-2.5 py-2 text-left transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-ring/40",
                 active ? "bg-[oklch(var(--primary)/0.12)]" : "hover:bg-accent",
               ].join(" ")}
             >