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/utils/workflow-utils.ts

@@ -15,8 +15,8 @@ import type { Workflow } from "@/types/workflow";
 import { getTypedWorkflow } from "@/types/workflow";
 
 /**
- * Detects if a JSON schema represents a ChatMessage input type.
- * ChatMessage schemas typically have:
+ * Detects if a JSON schema represents a Message input type.
+ * Message schemas typically have:
  * - type: "object"
  * - properties with "text" (required string) and "role" (optional string)
  *
@@ -24,7 +24,7 @@ import { getTypedWorkflow } from "@/types/workflow";
  * component for workflows that start with an AgentExecutor.
  *
  * @param schema - The JSON schema to check
- * @returns true if the schema represents a ChatMessage-like input
+ * @returns true if the schema represents a Message-like input
  */
 export function isChatMessageSchema(schema: JSONSchemaProperty | undefined): boolean {
   if (!schema) return false;
@@ -37,13 +37,13 @@ export function isChatMessageSchema(schema: JSONSchemaProperty | undefined): boo
 
   const props = schema.properties;
 
-  // ChatMessage has "text" property (the main content)
+  // Message has "text" property (the main content)
   const hasText = "text" in props && props.text?.type === "string";
 
-  // ChatMessage has "role" property (user, assistant, system)
+  // Message has "role" property (user, assistant, system)
   const hasRole = "role" in props && props.role?.type === "string";
 
-  // If it has both text and role, it's likely a ChatMessage
+  // If it has both text and role, it's likely a Message
   if (hasText && hasRole) {
     return true;
   }