🔀 refactor: Conditional Mapping Support for Multi-Convo (Parallel) Messages (#11180)

* refactor: message handling with addedConvo support

- Introduced `addedConvo` property in message schema to track conversation additions.
- Updated `BaseClient` to conditionally include `addedConvo` in saved messages based on request body.
- Enhanced `AgentClient` to apply mapping logic for messages with the `addedConvo` flag, improving message processing.
- Updated documentation to reflect new optional `mapCondition` parameter for message mapping functions, enhancing flexibility in message handling.

* test: Add comprehensive tests for getMessagesForConversation method

- Introduced a suite of tests for the `getMessagesForConversation` method in the `AgentClient` to validate mapping logic based on `mapMethod` and `mapCondition`.
- Covered various scenarios including applying mapping to all messages, conditional mapping based on `addedConvo`, handling of empty messages, and preserving message order.
- Ensured robust handling of edge cases such as null `mapMethod` and undefined `mapCondition`, enhancing overall test coverage and reliability of message processing.

api/server/controllers/agents/client.js

@@ -361,14 +361,13 @@ class AgentClient extends BaseClient {
     { instructions = null, additional_instructions = null },
     opts,
   ) {
-    const hasAddedConvo = this.options.req?.body?.addedConvo != null;
+    /** Always pass mapMethod; getMessagesForConversation applies it only to messages with addedConvo flag */
     const orderedMessages = this.constructor.getMessagesForConversation({
       messages,
       parentMessageId,
       summary: this.shouldSummarize,
-      mapMethod: hasAddedConvo
-        ? createMultiAgentMapper(this.options.agent, this.agentConfigs)
-        : undefined,
+      mapMethod: createMultiAgentMapper(this.options.agent, this.agentConfigs),
+      mapCondition: (message) => message.addedConvo === true,
     });
 
     let payload;