feat(qwen36-vl): split thinking — non-thinking default + qwen3.6-35b-a3b-thinking variant

The qwen3.6-35b-a3b VL checkpoint is a single hybrid model with a per-
request enable_thinking switch (Qwen3-style), defaulting thinking ON.
Make the default non-thinking and add an opt-in reasoning variant,
mirroring the existing glm-5.1 / glm-5.1-reasoning gateway split.

- qwen36-vl compose: add --reasoning-parser qwen3 (model-matched) so the
  single :8007 endpoint splits <think> into reasoning_content when on and
  routes all output to content when off — serving both modes cleanly.
- litellm gateway: base qwen3.6-35b-a3b pins chat_template_kwargs
  enable_thinking=false (non-thinking default); new qwen3.6-35b-a3b-thinking
  pins enable_thinking=true (opt-in reasoning). Same upstream checkpoint,
  no extra VRAM/container.

Deployed + verified on ana-ml2 (vLLM recreated, healthy) and ana-docker
(litellm reloaded): default returns a direct answer with no reasoning_content;
-thinking returns cleanly-separated reasoning_content, no raw tag leak.

stacks/litellm/conf/config.yaml

@@ -33,12 +33,37 @@ model_list:
   # --- Qwen3.6-35B-A3B vision-language MoE (official FP8) — vision + chat. vLLM
   #     on ana-ml2 GPU 1, :8007. Explicit entry shadows the "*" wildcard llama-swap
   #     route. REPLACED qwen3.5-9b-fp8 2026-06-14 (the 9B is retired; this is a
-  #     35B-A3B MoE — served under its TRUE name, never aliased under the old one). ---
+  #     35B-A3B MoE — served under its TRUE name, never aliased under the old one).
+  #
+  #     THINKING SPLIT (2026-06-15, operator call — mirrors the glm-5.1 pattern
+  #     above). One hybrid checkpoint; the per-request `enable_thinking` switch
+  #     picks the mode. LiteLLM forwards extra_body verbatim to vLLM, where
+  #     chat_template_kwargs lands in the chat template. vLLM runs
+  #     --reasoning-parser qwen3 so reasoning surfaces as reasoning_content. ---
+  # qwen3.6-35b-a3b: thinking DISABLED by default. The checkpoint defaults
+  #   thinking ON; enable_thinking=false forces the empty <think></think> block.
+  #   Reasoning is opt-in via qwen3.6-35b-a3b-thinking below.
   - model_name: qwen3.6-35b-a3b
     litellm_params:
       model: hosted_vllm/qwen3.6-35b-a3b
       api_base: http://10.250.50.54:8007/v1
       api_key: os.environ/VLLM_API_KEY
+      extra_body:
+        chat_template_kwargs:
+          enable_thinking: false
+    model_info:
+      mode: chat
+  # qwen3.6-35b-a3b-thinking: identical upstream checkpoint, thinking ENABLED
+  #   (opt-in reasoning). The qwen3 reasoning-parser splits <think>…</think> into
+  #   reasoning_content; content holds just the answer.
+  - model_name: qwen3.6-35b-a3b-thinking
+    litellm_params:
+      model: hosted_vllm/qwen3.6-35b-a3b
+      api_base: http://10.250.50.54:8007/v1
+      api_key: os.environ/VLLM_API_KEY
+      extra_body:
+        chat_template_kwargs:
+          enable_thinking: true
     model_info:
       mode: chat