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/tui/src/view/overlays/mod.rs

@@ -4,6 +4,7 @@
 
 pub mod bash;
 pub mod clear_confirm;
+pub mod diff;
 pub mod editor;
 pub mod effort;
 pub mod help;
@@ -123,5 +124,8 @@ pub fn render_overlay(
         Overlay::ClearConfirm => {
             clear_confirm::render(frame, overlay_area, block, state);
         }
+        Overlay::Diff => {
+            diff::render(frame, overlay_area, block, state);
+        }
     }
 }