feat(spa): keep player in sync across next-round and document issue-180 flow

docs/issue-180-flow-log.md

@@ -0,0 +1,28 @@
+# Issue #180 – SPA gameplay flow evidence
+
+## Flow log (host + player, no page reload)
+
+1. Host opens SPA host shell and loads scoreboard (`GET /lobby/sessions/{code}/scoreboard`).
+2. Host starts next round (`POST /lobby/sessions/{code}/rounds/next`).
+3. Host shell refreshes session state in-place (`GET /lobby/sessions/{code}`) and clears old scoreboard/final leaderboard payloads.
+4. Player shell performs periodic session refresh while online (3s cadence) and transitions from `scoreboard` to `lobby` without page reload.
+5. Host finishes game (`POST /lobby/sessions/{code}/finish`) and renders final leaderboard directly in SPA shell.
+6. Player shell reads `finished` state and renders final leaderboard in SPA (sorted by score).
+7. Error/retry paths available:
+   - Host: next-round and finish-game retry buttons with explicit error feedback.
+   - Player: reconnect + submit retry feedback.
+
+## Test output snapshot
+
+Command:
+
+```bash
+cd frontend/angular
+npm test -- --run src/app/features/host/host-shell.component.spec.ts src/app/features/player/player-shell.component.spec.ts
+```
+
+Result:
+
+- `host-shell.component.spec.ts`: 6 passed
+- `player-shell.component.spec.ts`: 7 passed
+- Total: 13 passed, 0 failed

frontend/angular/src/app/features/player/player-shell.component.spec.ts

@@ -198,6 +198,30 @@ describe('PlayerShellComponent gameplay wiring', () => {
     expect(fetchMock).toHaveBeenCalledTimes(3);
   });
 
+  it('auto-refreshes player session to avoid host/player state desync between rounds', async () => {
+    vi.useFakeTimers();
+
+    const fetchMock: FetchMock = vi
+      .fn()
+      .mockResolvedValueOnce(jsonResponse(200, sessionDetailPayload('scoreboard', { roundQuestionId: null })))
+      .mockResolvedValueOnce(jsonResponse(200, sessionDetailPayload('lobby', { roundQuestionId: null })));
+
+    vi.stubGlobal('fetch', fetchMock);
+
+    const component = new PlayerShellComponent();
+    component.sessionCode = 'ABCD12';
+
+    await component.refreshSession();
+    expect(component.session?.session.status).toBe('scoreboard');
+
+    await vi.advanceTimersByTimeAsync(3100);
+
+    expect(fetchMock).toHaveBeenCalledTimes(2);
+    expect(component.session?.session.status).toBe('lobby');
+
+    component.ngOnDestroy();
+  });
+
   it('enters reconnecting state when network request fails while online', async () => {
     vi.stubGlobal('navigator', { onLine: true });
 

frontend/angular/src/app/features/player/player-shell.component.ts

@@ -107,6 +107,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
   private readonly sessionContextStore = createSessionContextStore(resolveLocalStorage());
   private readonly controller = createVerticalSliceController(createApiClient(), this.sessionContextStore);
   private reconnectTimer: ReturnType<typeof setTimeout> | null = null;
+  private stateSyncTimer: ReturnType<typeof setTimeout> | null = null;
 
   constructor() {
     if (typeof navigator !== 'undefined' && !navigator.onLine) {
@@ -145,6 +146,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
       window.removeEventListener('offline', this.handleOffline);
     }
     this.clearReconnectTimer();
+    this.clearStateSyncTimer();
   }
 
   private readonly handleOnline = (): void => {
@@ -155,6 +157,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
   private readonly handleOffline = (): void => {
     this.connectionState = 'offline';
     this.clearReconnectTimer();
+    this.clearStateSyncTimer();
   };
 
   private clearReconnectTimer(): void {
@@ -164,6 +167,34 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     }
   }
 
+  private clearStateSyncTimer(): void {
+    if (this.stateSyncTimer) {
+      clearTimeout(this.stateSyncTimer);
+      this.stateSyncTimer = null;
+    }
+  }
+
+  private scheduleStateSync(): void {
+    this.clearStateSyncTimer();
+
+    if (!this.sessionCode.trim() || this.connectionState !== 'online' || !this.session) {
+      return;
+    }
+
+    if (this.session.session.status === 'finished') {
+      return;
+    }
+
+    this.stateSyncTimer = setTimeout(() => {
+      this.stateSyncTimer = null;
+      if (this.loading || this.connectionState !== 'online') {
+        this.scheduleStateSync();
+        return;
+      }
+      void this.refreshSession();
+    }, 3000);
+  }
+
   get loadingMessage(): string {
     switch (this.loadingTransition) {
       case 'join':
@@ -192,9 +223,12 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
   private markOnline(): void {
     this.connectionState = 'online';
     this.clearReconnectTimer();
+    this.scheduleStateSync();
   }
 
   private markConnectionIssue(error: unknown): void {
+    this.clearStateSyncTimer();
+
     if (typeof navigator !== 'undefined' && !navigator.onLine) {
       this.connectionState = 'offline';
       return;