fix(debugger): keep the selected tab when a step finishes

Every pause brought Threads & Variables to the front, so stepping from the
Console tab switched away from the output after each Step Over. Only a stop
at a breakpoint, exception or pause request does that now; finishing a step
keeps the tab the user is on.

Refs #2494

src/features/debugger/__tests__/toolWindow.test.tsx

@@ -134,6 +134,11 @@ describe("debug tool window", () => {
     expect(console.getAttribute("aria-selected")).toBe("true");
     act(() => useDebug.setState({ sessions: { 1: session } }));
     expect(variables.getAttribute("aria-selected")).toBe("true");
+    // Stepping from the Console keeps it in front.
+    fireEvent.click(console);
+    act(() => useDebug.setState({ sessions: { 1: { ...session, status: "running" } } }));
+    act(() => useDebug.setState({ sessions: { 1: { ...session, stopReason: "step" } } }));
+    expect(console.getAttribute("aria-selected")).toBe("true");
   });
 
   it("renders session tabs, views, frames and typed variables", async () => {

src/features/debugger/ui/DebugToolWindow.tsx

@@ -153,7 +153,14 @@ export function DebugToolWindow() {
     setView({
       session: active.startedAt,
       status: active.status,
-      tab: active.status === "starting" ? "console" : active.status === "paused" ? "variables" : view.tab,
+      // A breakpoint or exception brings Threads & Variables to the front; finishing a step keeps
+      // the tab the user is on (e.g. Console, to watch the output while stepping).
+      tab:
+        active.status === "starting"
+          ? "console"
+          : active.status === "paused" && active.stopReason !== "step"
+            ? "variables"
+            : view.tab,
     });
   const tab = view.tab;