feat: add semantic search tool for code symbol indexing and searching

- Implemented a new tool for semantic code search that indexes Rust code symbols (functions, structs, enums, traits, modules) and allows searching by name, concept, or meaning.
- Introduced a symbol index structure with methods for rebuilding the index and searching symbols.
- Added regex patterns for extracting various code symbols from Rust source files.
- Implemented scoring logic for search results based on exact matches, prefix matches, and context relevance.
- Created a web search tool that interacts with a SearXNG instance to fetch documentation and API information based on user queries.
- Added a diff preview overlay for rendering git diff output with color-coded additions and deletions in a TUI interface.

apps/interfaces/daemon/src/handler.rs

@@ -330,6 +330,8 @@ fn handle_submit_input(state: &mut AppStateRest, text: String) {
         api_key,
         model: state.settings.model.clone(),
         api_base: provider_cfg.map(|cfg| cfg.api_base.clone()),
+        edit_count: 0,
+        consecutive_empty_reviews: 0,
     };
 
     zesdex_infrastructure::agent::spawn_agent_turn(params);