fix(lotus): explain a failed voice connection and offer Try again

"Failed to connect to Livekit server (Reason: ServerUnreachable)" left a
user with nothing to try; they retried for a long time and gave up.

- Title "Couldn't connect to voice". The message depends on the reason:
  unreachable/timeout-style errors explain that voice needs its own live
  connection, which VPNs, antivirus web shields and some networks block,
  even when chat works, and say what to try; NotAllowed says the call may
  be full or access changed.
- The raw reason, status and message move under Technical details.
- LivekitConnectionError and PeerConnectionTimeoutError now get a
  Try again button (the existing reconnect path), shown as primary: the
  Lotus theme renders `secondary` as dark-on-dark.

Verified in the Lotus client against a local LiveKit with the signal
socket and validate request blocked: the dialog appears after ~20 s;
unblocking and pressing Try again joins with the mic published.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/room/GroupCallErrorBoundary.test.tsx

@@ -365,17 +365,18 @@ describe("LiveKit ConnectionError variants", () => {
       expectedReason: "InternalError",
     },
   ])(
-    "should display LiveKit $name error correctly",
+    "should explain the LiveKit $name error and offer a retry",
     async ({ error, expectedReason }) => {
       const TestComponent = (): ReactNode => {
         throw new LivekitConnectionError(error);
       };
+      const recoveryActionHandler = vi.fn(async () => Promise.resolve());
 
       const { asFragment } = render(
         <BrowserRouter>
           <GroupCallErrorBoundary
             onError={vi.fn()}
-            recoveryActionHandler={vi.fn()}
+            recoveryActionHandler={recoveryActionHandler}
             widget={null}
           >
             <TestComponent />
@@ -383,12 +384,28 @@ describe("LiveKit ConnectionError variants", () => {
         </BrowserRouter>,
       );
 
-      // Check title
-      await screen.findByText("Failed to connect to Livekit server");
+      await screen.findByText("Couldn’t connect to voice");
 
-      // Check that reason is displayed in the description
-      expect(screen.getByText(/Reason:/i)).toBeInTheDocument();
-      expect(screen.getByText(expectedReason)).toBeInTheDocument();
+      // [lotus] Plain-language guidance instead of "(Reason: X)".
+      expect(
+        screen.getByText(
+          expectedReason === "NotAllowed"
+            ? /The voice server didn’t let you in/
+            : /Your device couldn’t reach the voice server/,
+        ),
+      ).toBeInTheDocument();
+
+      // The raw reason is still there, under Technical details.
+      expect(screen.getByText("Technical details")).toBeInTheDocument();
+      expect(
+        screen.getByText(new RegExp(`Reason: ${expectedReason}`), {
+          selector: "pre",
+        }),
+      ).toBeInTheDocument();
+
+      // Try again re-enters the call.
+      await userEvent.click(screen.getByRole("button", { name: "Try again" }));
+      expect(recoveryActionHandler).toHaveBeenCalledWith("reconnect");
 
       expect(asFragment()).toMatchSnapshot();
     },