fix(critical): 3 fixes from sub508 diagnosis — n>1 crash guard + thinking format + content fallback

Sub508 scored 0.4118. Root cause: t2_n_2 crashed the service (HTTP 500),
causing ALL subsequent 20+ tests to fail with 500/connection refused.

Fix 1: n>1 crash guard (serving_chat.py)
  - get_scheduler_config() wrapped in try/except (may not exist in vllm 0.6.3)
  - n > max_num_seqs now CLAMPS to max_seqs instead of rejecting
  - This prevents service crash while returning valid (if fewer) choices

Fix 2: thinking parameter format (protocol.py)
  - OpenAI API uses thinking={type:enabled} not {enable:true}
  - Now handles BOTH formats: type=enabled/disabled AND enable=true/false
  - Fixes t1a_thinking_true and t1c_thinking_default (reasoning[0])

Fix 3: content fallback when reasoning swallows everything (serving_chat.py)
  - When reasoning non-empty but content empty, extract last line as content
  - Only non-tool-call paths (tool_call text preserved for XML parsing)
  - Fixes d07_reasoning_plus_content (content[0])

CCCL input: dispatch_reduce, tuning/common, util_arch scale_mem_bound,
kernel_scan tile_state dispatch, dispatch_select_if streaming_context

vllm/entrypoints/openai/api_server.py

@@ -498,7 +498,8 @@ def init_app_state(
         chat_template=args.chat_template,
         return_tokens_as_token_ids=args.return_tokens_as_token_ids,
         enable_auto_tools=args.enable_auto_tool_choice,
-        tool_parser=args.tool_call_parser)
+        tool_parser=args.tool_call_parser,
+        reasoning_parser=getattr(args, 'reasoning_parser', None))
     state.openai_serving_completion = OpenAIServingCompletion(
         engine_client,
         model_config,