refactor: DB-driven agent output events with single emission point

DB log chunk insertion is now the sole trigger for agent:output events.
Eliminates triple emission (FileTailer, handleStreamEvent, output buffer)
in favor of: FileTailer.onRawContent → DB insert → EventBus emit.

- createLogChunkCallback emits agent:output after successful DB insert
- spawnInternal now wires onRawContent callback (fixes session 1 gap)
- Remove eventBus from FileTailer (no longer touches EventBus)
- Remove eventBus from ProcessManager constructor (dead parameter)
- Remove agent:output emission from handleStreamEvent text_delta
- Remove outputBuffers map and all buffer helpers from manager/handler
- Remove getOutputBuffer from AgentManager interface and implementations
- getAgentOutput tRPC: DB-only, no file fallback
- onAgentOutput subscription: no initial buffer yield, events only
- AgentOutputViewer: accumulates raw JSONL chunks, parses uniformly

packages/web/src/components/AgentOutputViewer.tsx

@@ -21,6 +21,8 @@ export function AgentOutputViewer({ agentId, agentName, status, onStop }: AgentO
   const [messages, setMessages] = useState<ParsedMessage[]>([]);
   const [follow, setFollow] = useState(true);
   const containerRef = useRef<HTMLDivElement>(null);
+  // Accumulate raw JSONL: initial query data + live subscription chunks
+  const rawBufferRef = useRef<string>('');
 
   // Load initial/historical output
   const outputQuery = trpc.getAgentOutput.useQuery(
@@ -37,8 +39,9 @@ export function AgentOutputViewer({ agentId, agentName, status, onStop }: AgentO
       onData: (event: any) => {
         // TrackedEnvelope shape: { id, data: { agentId, data: string } }
         const raw = event?.data?.data ?? event?.data;
-        const data = typeof raw === 'string' ? raw : JSON.stringify(raw);
-        setMessages((prev) => [...prev, { type: 'text', content: data }]);
+        const chunk = typeof raw === 'string' ? raw : JSON.stringify(raw);
+        rawBufferRef.current += chunk;
+        setMessages(parseAgentOutput(rawBufferRef.current));
       },
       onError: (error) => {
         console.error('Agent output subscription error:', error);
@@ -51,12 +54,14 @@ export function AgentOutputViewer({ agentId, agentName, status, onStop }: AgentO
   // Set initial output when query loads
   useEffect(() => {
     if (outputQuery.data) {
+      rawBufferRef.current = outputQuery.data;
       setMessages(parseAgentOutput(outputQuery.data));
     }
   }, [outputQuery.data]);
 
   // Reset output when agent changes
   useEffect(() => {
+    rawBufferRef.current = '';
     setMessages([]);
     setFollow(true);
   }, [agentId]);