feat: implement mandatory explore phase with parallel subagents

- Added `ExploreService` trait and `ExploreServiceImpl` struct to handle the exploration of codebase context before agent turns.
- Implemented three parallel subagents: Code Structure, Symbol Index, and Semantic Context, each with specific directives.
- Integrated the explore phase into the agent turn process, ensuring that each turn starts with a consolidated context message.
- Enhanced `spawn_agent_turn` function to include explore service wiring and context preparation.

apps/interfaces/tui/src/turn.rs

@@ -110,6 +110,11 @@ pub fn spawn_agent_turn(state: &mut AppStateRest, text: String) {
         api_base: api_base.clone(),
     };
 
+    // Clone credentials before moving into LlmClient.
+    let explore_api_key = api_key.clone();
+    let explore_model = model.clone();
+    let explore_base_url = api_base.clone().unwrap_or_else(|| "https://api.openai.com/v1".to_string());
+
     let client = std::sync::Arc::new(LlmClient::new(api_key, model, api_base));
 
     let tool_ctx = ToolCtx::builder()
@@ -118,13 +123,30 @@ pub fn spawn_agent_turn(state: &mut AppStateRest, text: String) {
         .turn_events(turn_events)
         .build();
 
+    // Clone ToolCtx for the explore service (before moving into executor).
+    let explore_ctx = tool_ctx.clone();
+
     let tool_executor =
         std::sync::Arc::new(InfrastructureToolExecutor::new(tool_ctx));
 
     let tools = all_tools();
     let defs = tool_defs(&tools);
 
-    let turn_service = AgentTurnServiceImpl::new(client, tool_executor, defs);
+    // Wire the mandatory explore phase (3+ parallel subagents).
+    let explore_creds = zesdex_infrastructure::best_practice::explore::Credentials {
+        base_url: explore_base_url,
+        api_key: explore_api_key,
+        model: explore_model,
+    };
+    let explore_service = std::sync::Arc::new(
+        zesdex_infrastructure::best_practice::explore::ExploreServiceImpl::new(
+            explore_ctx,
+            explore_creds,
+        ),
+    );
+
+    let turn_service = AgentTurnServiceImpl::new(client, tool_executor, defs)
+        .with_explore(explore_service);
 
     tokio::spawn(async move {
         let _ = turn_service.run_turn(params).await;