fix(server,web): live in-progress output survives refresh and reconnect (#77)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/web/src/api/sse.ts

@@ -15,10 +15,15 @@ import type { OmniMessage } from "@prismshadow/penguin-core/omnimessage";
 import type { ServerEvent } from "@prismshadow/penguin-server/api";
 
 export interface StreamHandlers {
-  /** A single OmniMessage (full/streaming/event, envelope as-is). */
-  onOmniMessage: (msg: OmniMessage) => void;
-  /** A single server event. */
-  onServerEvent: (event: ServerEvent) => void;
+  /**
+   * A single OmniMessage (full/streaming/event, envelope as-is). `eventId` is the SSE
+   * event id assigned by the server channel (`<epoch>-<seq>`; null if the event carried
+   * none) — stream-controller uses it to align buffered events with the live-tail cursor
+   * that GET /messages returns.
+   */
+  onOmniMessage: (msg: OmniMessage, eventId: string | null) => void;
+  /** A single server event (`eventId`: same as onOmniMessage). */
+  onServerEvent: (event: ServerEvent, eventId: string | null) => void;
   /** Connection established (including a successful auto-reconnect). */
   onOpen?: () => void;
   /**
@@ -37,14 +42,15 @@ function subscribe(url: string, handlers: StreamHandlers): StreamConnection {
   const source = new EventSource(url);
   source.onmessage = (e: MessageEvent<string>) => {
     try {
-      handlers.onOmniMessage(JSON.parse(e.data) as OmniMessage);
+      // Every server event carries an `id:` line; lastEventId is "" only if none did.
+      handlers.onOmniMessage(JSON.parse(e.data) as OmniMessage, e.lastEventId || null);
     } catch {
       // Ignore lines that fail to parse (the protocol guarantees single-line JSON data, so this shouldn't normally happen).
     }
   };
   source.addEventListener("server_event", (e: MessageEvent<string>) => {
     try {
-      handlers.onServerEvent(JSON.parse(e.data) as ServerEvent);
+      handlers.onServerEvent(JSON.parse(e.data) as ServerEvent, e.lastEventId || null);
     } catch {
       // Same as above.
     }