Python: [BREAKING] Simplify API: ChatAgent -> Agent, ChatMessage -> Message (#3747)

* [BREAKING] Rename ChatAgent -> Agent, ChatMessage -> Message, ChatClientProtocol -> SupportsChatGetResponse

Simplify the public API by removing redundant 'Chat' prefix from core types:
- ChatAgent -> Agent
- RawChatAgent -> RawAgent
- ChatMessage -> Message
- ChatClientProtocol -> SupportsChatGetResponse

Also renamed internal WorkflowMessage (was Message in _runner_context) to avoid collision.

No backward compatibility aliases - this is a clean breaking change.

* [BREAKING] Rename Agent chat_client parameter to client

* Fix rebase issues: WorkflowMessage references and broken markdown links

* Fix formatting and lint issues from code quality checks

* Fix import ordering in workflow sample files

* fixed rebase

* Fix test failures: use WorkflowMessage and A2AMessage after ChatMessage→Message rename

- Replace Message(data=..., source_id=...) with WorkflowMessage(...) in workflow tests
- Fix isinstance check in A2A agent to use A2AMessage instead of Message
- Fix import in test_workflow_observability.py (Message→WorkflowMessage)

* Fix lint, fmt, and sample errors after ChatMessage→Message rename

- Auto-fix 70+ ruff lint issues across samples (ChatMessage→Message refs)
- Fix HostedVectorStoreContent→Content.from_hosted_vector_store in file search sample
- Fix _normalize_messages→normalize_messages in custom agent sample
- Fix context.terminate→raise MiddlewareTermination in middleware samples
- Fix with_update_hook→with_transform_hook in override middleware sample
- Add TOptions_co import back to custom_chat_client sample
- Add noqa for FastAPI File() default in chatkit sample
- Fix B023 loop variable capture in weather agent sample

* fix: update Agent constructor calls from chat_client to client in declaration-only tool tests

* fix: add register_cleanup to devui lazy-loading proxy and type stub

* fixed tests and updated new pieces

* fix agui typevar

* fix merge errors

* fix merge conflicts

* fiux merge

* Remove unused links

---------

Co-authored-by: Evan Mattson <evan.mattson@microsoft.com>

python/packages/devui/frontend/src/components/features/workflow/run-workflow-button.tsx

@@ -76,7 +76,7 @@ export function RunWorkflowButton({
 
   // Analyze input requirements
   const inputAnalysis = useMemo(() => {
-    // Check if this is a ChatMessage schema (for AgentExecutor workflows)
+    // Check if this is a Message schema (for AgentExecutor workflows)
     const isChatMessage = isChatMessageSchema(inputSchema);
 
     if (!inputSchema)

python/packages/devui/frontend/src/components/features/workflow/schema-form-renderer.tsx

@@ -115,7 +115,7 @@ export function getFieldColumnSpan(
 }
 
 // ============================================================================
-// ChatMessage Pattern Detection (exported for reuse)
+// Message Pattern Detection (exported for reuse)
 // ============================================================================
 
 export function detectChatMessagePattern(
@@ -436,7 +436,7 @@ export function SchemaFormRenderer({
     (name) => !hideFields.includes(name)
   );
 
-  // Detect ChatMessage pattern
+  // Detect Message pattern
   const isChatMessageLike = detectChatMessagePattern(schema, requiredFields);
 
   // Separate required and optional fields
@@ -449,7 +449,7 @@ export function SchemaFormRenderer({
     (name) => !requiredFields.includes(name)
   );
 
-  // For ChatMessage: prioritize text/message/content
+  // For Message: prioritize text/message/content
   const sortedOptionalFields = isChatMessageLike
     ? [...optionalFieldNames].sort((a, b) => {
         const priority = (name: string) =>

python/packages/devui/frontend/src/components/features/workflow/workflow-input-form.tsx

@@ -48,7 +48,7 @@ export function WorkflowInputForm({
   const requiredFields = inputSchema.required || [];
   const isSimpleInput = inputSchema.type === "string" && !inputSchema.enum;
 
-  // Detect ChatMessage-like pattern for auto-filling role
+  // Detect Message-like pattern for auto-filling role
   const isChatMessageLike = detectChatMessagePattern(inputSchema, requiredFields);
 
   // Validation: check if required fields are filled
@@ -82,7 +82,7 @@ export function WorkflowInputForm({
         }
       });
 
-      // Auto-fill role="user" for ChatMessage-like inputs
+      // Auto-fill role="user" for Message-like inputs
       if (isChatMessageLike && !initialData["role"]) {
         initialData["role"] = "user";
       }

python/packages/devui/frontend/src/components/layout/debug-panel.tsx

@@ -1340,7 +1340,7 @@ function TraceTreeNode({ node, depth = 0 }: { node: TraceNode; depth?: number })
 
         {/* Operation badge */}
         <span className={`text-xs px-1.5 py-0.5 rounded font-medium ${getOperationColor(operationName)}`}>
-          {operationName.replace("ChatAgent.", "").replace("invoke_agent ", "")}
+          {operationName.replace("Agent.", "").replace("invoke_agent ", "")}
         </span>
 
         {/* Duration */}