batch3 T3: broker user channel + /api/ws/user + project/session/inference emits

- broker.subscribeUser/publishUser via separate user topics map
- /api/ws/user WS route subscribes to the user channel
- projects/sessions POST/DELETE handlers emit lifecycle frames
- inference 3 terminal-state sites emit session_updated with RETURNING

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/server/src/services/broker.ts

@@ -4,35 +4,53 @@ export type Listener = (frame: Frame) => void;
 export interface Broker {
   publish(sessionId: string, frame: Frame): void;
   subscribe(sessionId: string, listener: Listener): () => void;
+  publishUser(user: string, frame: Frame): void;
+  subscribeUser(user: string, listener: Listener): () => void;
 }
 
 export function createBroker(): Broker {
   const topics = new Map<string, Set<Listener>>();
+  const userTopics = new Map<string, Set<Listener>>();
+
+  function publishTo(map: Map<string, Set<Listener>>, key: string, frame: Frame): void {
+    const set = map.get(key);
+    if (!set) return;
+    for (const listener of set) {
+      try {
+        listener(frame);
+      } catch {
+        // ignore listener errors so one bad subscriber doesn't break the rest
+      }
+    }
+  }
+
+  function subscribeTo(map: Map<string, Set<Listener>>, key: string, listener: Listener): () => void {
+    let set = map.get(key);
+    if (!set) {
+      set = new Set();
+      map.set(key, set);
+    }
+    set.add(listener);
+    return () => {
+      const s = map.get(key);
+      if (!s) return;
+      s.delete(listener);
+      if (s.size === 0) map.delete(key);
+    };
+  }
+
   return {
     publish(sessionId, frame) {
-      const set = topics.get(sessionId);
-      if (!set) return;
-      for (const listener of set) {
-        try {
-          listener(frame);
-        } catch {
-          // ignore listener errors so one bad subscriber doesn't break the rest
-        }
-      }
+      publishTo(topics, sessionId, frame);
     },
     subscribe(sessionId, listener) {
-      let set = topics.get(sessionId);
-      if (!set) {
-        set = new Set();
-        topics.set(sessionId, set);
-      }
-      set.add(listener);
-      return () => {
-        const s = topics.get(sessionId);
-        if (!s) return;
-        s.delete(listener);
-        if (s.size === 0) topics.delete(sessionId);
-      };
+      return subscribeTo(topics, sessionId, listener);
+    },
+    publishUser(user, frame) {
+      publishTo(userTopics, user, frame);
+    },
+    subscribeUser(user, listener) {
+      return subscribeTo(userTopics, user, listener);
     },
   };
 }