fix: clean up orchestrator chat UX

- Tool call names now show human-readable labels ("Dispatched agent"
  instead of "spawn_agent"), deduped if called multiple times
- Model label only shown when a real value is returned; "unknown"
  and null are suppressed; model names shortened (GLM-5, Gemini)

Made-with: Cursor

app/api/projects/[projectId]/agent-chat/route.ts

@@ -74,7 +74,7 @@ export async function POST(
       reasoning: data.reasoning ?? null,
       toolCalls: data.toolCalls ?? [],
       turns: data.turns ?? 0,
-      model: data.model ?? "unknown",
+      model: data.model || null,
       sessionId,
     });
   } catch (err) {