fix(api): fix duplicate answer and completion app upgrade issues

1. Remove StreamChunkEvent from AgentV2Node._run_without_tools():
   The agent-v2 node was yielding StreamChunkEvent during LLM streaming,
   AND the downstream answer node was outputting the same text via
   {{#agent.text#}} variable reference, causing "FourFour" duplication.
   Now text only flows through outputs.text -> answer node (single path).

2. Map inputs to query for completion app transparent upgrade:
   Completion apps send {inputs: {query: "..."}} not {query: "..."}.
   VirtualWorkflowSynthesizer route now extracts query from inputs
   when the top-level query is missing.

Verified:
- Old chat app: "What is 2+2?" -> "Four" (was "FourFour")
- Old completion app: {inputs: {query: "What is 3+3?"}} -> "3 + 3 = 6" (was failing)
- Old agent-chat app: still works

Made-with: Cursor

api/core/workflow/nodes/agent_v2/node.py

@@ -170,10 +170,6 @@ class AgentV2Node(Node[AgentV2NodeData]):
                 chunk_text = self._extract_chunk_text(chunk)
                 if chunk_text:
                     full_text += chunk_text
-                    yield StreamChunkEvent(
-                        selector=[self._node_id, "text"],
-                        chunk=chunk_text,
-                    )
 
                 if chunk.delta.usage:
                     usage = chunk.delta.usage

api/services/app_generate_service.py

@@ -141,6 +141,12 @@ class AppGenerateService:
                         workflow.id,
                     )
 
+                    upgraded_args = dict(args)
+                    if "query" not in upgraded_args or not upgraded_args.get("query"):
+                        inputs = upgraded_args.get("inputs", {})
+                        upgraded_args["query"] = inputs.get("query", "") or inputs.get("input", "") or str(inputs)
+                    args = upgraded_args
+
                     if streaming:
                         with rate_limit_context(rate_limit, request_id):
                             payload = AppExecutionParams.new(