SSE en formato Claude Code CLI via ?format=claude

Nuevo ClaudeFormatEmitter traduce eventos nativos al formato exacto
que produce Claude Code CLI: content_block_start/delta/stop, tool_result,
assistant snapshots, result con usage/cost, done.

- streaming/claude_format.py: ClaudeFormatEmitter + DualEmitter
- base.py: enriquecer eventos con tool_call_id, raw_output, tool_arguments
- engine.py: usage/cost en EXECUTION_COMPLETED
- routes.py: ?format=claude en /sessions/{id}/stream
- main.py: DualEmitter wiring (emite a ambos formatos)

El frontend puede consumir el stream sin cambios — mismos event types
que Claude Code CLI. El formato nativo sigue disponible para el dashboard.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/orchestrator/engine.py

@@ -223,18 +223,6 @@ class OrchestratorEngine:
         final_content = self._assemble_response(results, review_result)
         status = "completed" if not failed_steps else "partial"
 
-        await self.sse.emit(
-            EventType.EXECUTION_COMPLETED,
-            {
-                "session_id": session.session_id,
-                "task_id": task.task_id,
-                "steps_completed": len(results),
-                "steps_failed": failed_steps,
-                "status": status,
-            },
-            session_id=session.session_id,
-        )
-
         # Accumulate token usage: planner + all steps + review
         total_input = planner_usage.get("input_tokens", 0)
         total_output = planner_usage.get("output_tokens", 0)
@@ -250,6 +238,23 @@ class OrchestratorEngine:
             + (total_output / 1_000_000) * settings.cost_per_1m_output
         )
 
+        await self.sse.emit(
+            EventType.EXECUTION_COMPLETED,
+            {
+                "session_id": session.session_id,
+                "task_id": task.task_id,
+                "steps_completed": len(results),
+                "steps_failed": failed_steps,
+                "status": status,
+                "usage": {
+                    "input_tokens": total_input,
+                    "output_tokens": total_output,
+                },
+                "total_cost_usd": round(cost_usd, 6),
+            },
+            session_id=session.session_id,
+        )
+
         return {
             "session_id": session.session_id,
             "task_id": task.task_id,