Chrome extension connection reliability improved

When the Chrome extension lost its connection to the CDP relay, developers were left with silent failures and opaque timeout errors. The relay would wait indefinitely without knowing why the connection died or whether recovery was possible.

The system now sends heartbeat pings every 5 seconds and expects a pong response within 15 seconds. If the browser stops responding, the connection is terminated immediately rather than waiting for a command to time out. When the extension disconnects, a typed error surfaces immediately—browser_closed, extension_disconnected, debugger_detached, network_error, or heartbeat_timeout—instead of a generic "WebSocket closed" message.

Most importantly, transient disconnections no longer kill the entire session. A 15-second grace window allows the extension to reconnect and resume where it left off. The relay preserves its tab cache and Playwright state, resynchronizes the tab list on reconnect, and continues without interruption.

The changes span the @n8n/mcp-browser package's CDP relay server and the @n8n/mcp-browser-extension, with error handling wired through to the connection layer so AI agents receive actionable messages when the browser dies mid-operation.