Fix Langfuse userId tracking: use start_span() instead of start_as_current_span()

start_as_current_span() returns a context manager, not a span object,
causing 'update_trace()' to fail with:
  '_AgnosticContextManager' object has no attribute 'update_trace'

Signed-off-by: sallyom <somalley@redhat.com>

Author: sallyom

components/runners/claude-code-runner/wrapper.py

@@ -208,8 +208,9 @@ async def _run_claude_agent_sdk(self, prompt: str):
                         user_id = os.getenv('USER_ID', '').strip()
                         user_name = os.getenv('USER_NAME', '').strip()
 
-                        # Start a span for this session (Langfuse SDK 3.x)
-                        langfuse_session_span = langfuse_client.start_as_current_span(
+                        # Start a trace for this session with userId (Langfuse SDK 3.x)
+                        # Use start_span() instead of start_as_current_span() for long-lived traces
+                        langfuse_session_span = langfuse_client.start_span(
                             name="claude_agent_session",
                             input={"prompt": prompt},
                             metadata={
@@ -219,7 +220,7 @@ async def _run_claude_agent_sdk(self, prompt: str):
                             },
                         )
 
-                        # Set userId on the trace (trace-level attribute, not span-level)
+                        # Set userId on the trace (trace-level attribute)
                         if user_id:
                             try:
                                 langfuse_session_span.update_trace(user_id=user_id)