Add initial_state SSE event for reconnect sync (Phase 3)

When a dashboard connects via SSE, it now receives the current terminal
state for all active sessions. This allows dashboards to immediately
display the full terminal content without waiting for new output.

src/server.ts

@@ -135,8 +135,26 @@ const server = Bun.serve<SessionData>({
         start(controller) {
           ctrl = controller;
           sseClients.add(controller);
-          // Send initial headers
+          // Send initial connection acknowledgment
           controller.enqueue(": connected\n\n");
+
+          // Send current terminal state for all active sessions
+          for (const [sessionId, termSession] of sessionTerminals.entries()) {
+            const session = getSession(sessionId);
+            if (!session || session.ended_at) continue;
+
+            // Serialize full terminal state as HTML
+            const html = serializeAsHTML(termSession);
+
+            // Send as initial_state event
+            const event: SSEEvent = {
+              type: "initial_state",
+              session_id: sessionId,
+              html,
+            };
+            const eventStr = `event: ${event.type}\ndata: ${JSON.stringify(event)}\n\n`;
+            controller.enqueue(eventStr);
+          }
         },
         cancel() {
           sseClients.delete(ctrl);

src/types.ts

@@ -157,6 +157,7 @@ export type ServerMessage =
 // SSE events (Server -> Dashboard)
 
 export type SSEEvent =
+  | { type: "initial_state"; session_id: number; html: string }
   | {
       type: "session_start";
       session_id: number;