Refactor subagent and workflow domain models; migrate access tiers and events to domain module

- Moved `AccessTier` and `SubagentEvent` enums to `zesdex_domain::subagent`.
- Consolidated workflow-related types into `zesdex_domain::workflow`.
- Updated references across the codebase to use the new domain models.
- Refactored tool execution logic to utilize a new `ToolExecutor` trait.
- Enhanced `AgentTurnService` to handle tool calls and events more effectively.
- Adjusted API handlers and state management to align with new domain structure.

apps/interfaces/api/src/handlers/chat.rs

@@ -121,7 +121,7 @@ pub async fn chat_completions_handler(
     let llm_client = if model == state.llm_client.model {
         &state.llm_client
     } else {
-        temp_client = zesdex_infrastructure::llm::LlmClient::new(
+        temp_client = zesdex_infrastructure::llm::provider::LlmClient::new(
             state.llm_client.api_key.clone(),
             model,
             Some(state.llm_client.base_url.clone()),
@@ -129,14 +129,14 @@ pub async fn chat_completions_handler(
         &temp_client
     };
 
+    use zesdex_application::ports::ProviderService;
     let (response, usage) = llm_client
-        .chat_with_tools_non_streaming(
+        .chat(
             &messages,
             None, // No tool definitions for basic chat
             req.max_tokens,
             req.temperature,
-            None, // No abort flag
-        )
+        ).await
         .map_err(|e| ApiError::ChatProxy(format!("LLM request failed: {e}")))?;
 
     let (prompt_tokens, completion_tokens) = usage.unwrap_or((0, 0));