perf: optimize reconnect flow - aggressive backoff (500ms→5s), reconnect UI status, 30s keepAlive

docs/ARCHITECTURE.md

@@ -40,10 +40,11 @@ Maintains continuous synchronized viewing when watching series:
 
 ## 5. Peer Lifecycle & Dual Heartbeat
 To maintain a clean room state and eliminate "Ghost Peers":
-- **Session Heartbeat (Background)**: Every 1 minute, `background.js` sends an "I'm alive" signal to the server. This keeps you in the room even if no video is playing.
+- **Session Heartbeat (Background)**: Every 30 seconds, `background.js` sends an "I'm alive" signal to the server. This keeps you in the room even if no video is playing.
 - **Video Heartbeat (Content)**: Every 15 seconds, `content.js` sends current playback metadata (time, title, state) if a video is found.
 - **Server Pruning**: The server runs a "Reaper" every 2 minutes. If a peer has sent **zero** activity (no events and no heartbeats) for 5 minutes, they are forcefully disconnected.
 - **Immediate Cleanup**: Rooms are deleted instantly when the last peer leaves or disconnects.
+- **Reconnect Strategy**: Aggressive backoff — 500ms base, 1.5x multiplier, capped at 5s. Max 20 attempts before marking as failed. Events are queued during disconnect and flushed after namespace rejoin.
 
 > [!CAUTION]
 > **Identity Rule**: Differentiate between `peerId` and `socket.id`. Use `socket.id` exclusively for ephemeral transport routing on the server. Use `peerId` exclusively for identity, state management, and room tracking across the stack.
@@ -54,7 +55,8 @@ KoalaSync uses a megaphone routing approach to minimize server logic:
 - **Storm Prevention**: When dispatching state updates in response to a new user joining (e.g., an active lobby state), ensure ONLY the initiator (or a designated leader) calls `emit()` to prevent $O(N)$ broadcast storms.
 
 ## 7. Security & Stability
-- **Service Worker Lifecycle**: Uses `chrome.alarms` to prevent the Manifest V3 service worker from suspending while in an active room.
+- **Service Worker Lifecycle**: Uses `chrome.alarms` (30s interval) to prevent the Manifest V3 service worker from suspending while in an active room. On wake, runtime state is restored from `chrome.storage.session` via `ensureState()`.
+- **Reconnect Visualization**: Badge shows "..." (orange) during reconnect. Popup displays "Reconnecting..." with attempt counter.
 - **Rate Limiting**: Server-side per-socket and per-IP rate limits to prevent sync-spamming or DoS.
 - **Noise Filtering**: Uses a curated blacklist of domains (Search Engines, Social Media) to declutter the "Target Tab" selector in the popup.
 - **Diagnostics**: A "Dev" tab provides real-time access to the underlying `<video>` state (`readyState`, `paused`, `currentTime`) for easier troubleshooting.

docs/HOW_IT_WORKS.md

@@ -155,7 +155,7 @@ While in a room, two heartbeats keep the session alive:
 
 | Heartbeat | Interval | Source | Purpose |
 |:----------|:---------|:-------|:--------|
-| **Background** | 1 minute | `background.js` | Signals "I'm still connected" and handles 5-min auto-reconnect fallback |
+| **Background** | 30 seconds | `background.js` | Signals "I'm still connected" and triggers aggressive reconnect (500ms base, max 5s) |
 | **Content** | 15 seconds | `content.js` | Sends video metadata: `currentTime`, `mediaTitle`, `playbackState`, `volume`, `muted` |
 
 - **Server Reaper**: Every 2 minutes, the server checks for peers with no activity for 5+ minutes and disconnects them ("dead peer pruning").

docs/ROADMAP.md

@@ -4,16 +4,13 @@ This document tracks planned features, improvements, and their implementation de
 
 ---
 
-## Antworten auf offenen Fragen
+## Offene technische Fragen
 
-### 1. Graceful Shutdown
-**Korrektur:** Der Server hat bereits Graceful Shutdown implementiert (`server/index.js:481-499`). Bei SIGTERM/SIGINT wird allen Clients eine Neustart-Nachricht gesendet, der HTTP-Server geschlossen und nach 5s erzwungen beendet. **Kein Handlungsbedarf.**
-
-### 6. Service Worker Fallback bei Room-State Verlust
+### 1. Service Worker Fallback bei Room-State Verlust
 Manifest V3 suspendiert den Service Worker nach ~30s Inaktivität. `chrome.alarms` weckt ihn auf, aber:
 - **Problem:** Wenn der SW neu startet, sind alle Variablen (`currentRoom`, `socket`, `isNamespaceJoined`) weg
-- **Aktueller Stand:** `chrome.storage.session` persistiert `currentRoom`, `peerId`, `eventQueue` — der SW stellt diese beim Start wieder her (`restoreSession()`)
-- **Lücke:** Der WebSocket muss neu aufgebaut werden. Das passiert automatisch via `connect()`, aber es gibt eine **Zeitlücke** von 2-5 Sekunden in der Events verloren gehen können. **Verbesserung:** Queue-Events während Reconnect, visualisiere "Reconnecting..." im Popup.
+- **Aktueller Stand:** `chrome.storage.session` persistiert `currentRoom`, `peerId`, `eventQueue` — der SW stellt diese beim Start wieder her (`ensureState()`)
+- **Gelöst:** WebSocket wird automatisch via `connect()` neu aufgebaut. Events werden während Reconnect gequeued und nach Namespace-Join geflushed. "Reconnecting..." Status wird im Popup + Badge angezeigt. KeepAlive-Alarm auf 30s reduziert. Reconnect-Backoff: 500ms Basis, max 5s (statt vorher 1s→30s).
 
 ### 7. Tests für Extensions
 Stimmt, sind aufwändig. Praktische Ansätze: