feat(theme): add tool_output color to themes

- Added a `tool_output` color to the `Theme` struct.
- Updated all built-in themes to include the new color.
- Modified the TUI to use the `tool_output` color for rendering tool output.

crates/owlen-core/src/tools/mod.rs

@@ -5,6 +5,7 @@ use async_trait::async_trait;
 use serde_json::Value;
 
 pub mod code_exec;
+pub mod fs_tools;
 pub mod registry;
 pub mod web_search;
 pub mod web_search_detailed;