Fix chat example/schema mismatches

paths/chat/chat.yml

@@ -34,9 +34,10 @@ post:
               user:
                 userId: "user-456"
                 type: LEARNER
-                detailPreference: MEDIUM
-                tonePreference: FRIENDLY
-                languagePreference: "en"
+                preference:
+                  detail: MEDIUM
+                  tone: FRIENDLY
+                  language: "en"
               messages:
                 - role: USER
                   content: "Give me a hint for my answer about polymorphism."
@@ -64,9 +65,10 @@ post:
               user:
                 userId: "user-321"
                 type: LEARNER
-                detailPreference: DETAILED
-                tonePreference: NEUTRAL
-                languagePreference: "en"
+                preference:
+                  detail: DETAILED
+                  tone: NEUTRAL
+                  language: "en"
                 taskProgress:
                   currentQuestionId: "question-321"
                   timeSpentOnQuestion: "30 minutes"
@@ -154,7 +156,7 @@ post:
           schema:
             $ref: "./schemas/ChatResponse.yml"
           examples:
-            minimalChatResponse:
+            minimalChat:
               summary: Minimal chat response
               value:
                 output:
@@ -168,7 +170,7 @@ post:
                     When you call `speak()` on an `Animal` reference, the appropriate subclass method is invoked
                     based on the actual object type at runtime.
                 metadata: null
-            chatWithLlmConfigResponse:
+            chatWithLlmConfig:
               summary: Chat response with LLM configuration
               value:
                 output:
@@ -186,7 +188,7 @@ post:
                     model: "gpt-5.2"
                     temperature: 0.7
                     outputTokens: 78
-            chatWithContextResponse:
+            chatWithContext:
               summary: Chat response with context
               value:
                 output:

paths/chat/schemas/ChatRequest.yml

@@ -26,6 +26,14 @@ properties:
       - "null"
     description: Optional educational context (e.g., course material, task context).
     additionalProperties: true
+    properties:
+      task:
+        description: Optional task grounding this conversation.
+        type:
+          - object
+          - "null"
+        allOf:
+          - $ref: "../../shared/schemas/Task.yml"
   configuration:
     type:
       - object

paths/evaluate/evaluate.yml

@@ -98,18 +98,19 @@
               user:
                 userId: "user-789"
                 type: LEARNER
-                detailPreference: DETAILED
-                tonePreference: FRIENDLY
-                languagePreference: "en"
+                preference:
+                  detail: DETAILED
+                  tone: FRIENDLY
+                  language: "en"
               criteria:
                 - criterionId: "crit-1"
                   name: "Correctness"
                   context: "The explanation of polymorphism is conceptually correct."
                   maxPoints: 10
                 - criterionId: "crit-2"
                   name: "Clarity"
                   context: "The explanation is clear, well-structured, and easy to understand."
                   maxPoints: 5
               preSubmissionFeedback:
                 enabled: false
               configuration: