refactor: deepen modules, consolidate inference, delete dead code

- Extract build_graph/load_config/create_renderer in presentation (393→~250 lines)
- Move module inference into ModuleName::from_path(), delete 3 scattered copies
- Move resolve_relationships/filter_external_imports into CodeGraph
- Add LanguageExtractor trait in tree-sitter adapter
- Add CodeGraph::elements_by_module(), replace 6 identical grouping loops
- Delete dead RenderDiagrams query

crates/adapters/cargo-workspace/src/cargo_workspace_analyzer.rs

@@ -82,7 +82,7 @@ impl ProjectAnalyzer for CargoWorkspaceAnalyzer {
             let mut element =
                 CodeElement::new(package_name, CodeElementKind::Project, file_path, 1)?;
 
-            if let Some(module) = infer_group(member_path) {
+            if let Some(module) = ModuleName::from_directory_group(member_path) {
                 element = element.with_module(module);
             }
 
@@ -110,14 +110,3 @@ impl ProjectAnalyzer for CargoWorkspaceAnalyzer {
         Ok(graph)
     }
 }
-
-fn infer_group(member_path: &str) -> Option<ModuleName> {
-    let parts: Vec<&str> = member_path.split('/').collect();
-    if parts.len() < 3 {
-        return None;
-    }
-
-    let group = parts[parts.len() - 2];
-    let capitalized = format!("{}{}", group[..1].to_uppercase(), &group[1..]);
-    ModuleName::new(&capitalized).ok()
-}