refactor: move scattered business logic into domain

- CodeGraph::merge_project_edges() replaces presentation-layer function
- Language::is_test_file() centralises test file detection (was in walkdir)
- AnalysisConfig::is_standard_excluded() centralises default dir exclusions (was in walkdir)
- normalize_cargo_package() / normalize_python_package() in domain replace duplicated normalisers in each adapter
- walkdir, cargo-workspace, python-project updated to call domain methods

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

@@ -5,7 +5,7 @@ use serde::Deserialize;
 
 use archlens_domain::{
     CodeElement, CodeElementKind, CodeGraph, DomainError, FilePath, ModuleName, Relationship,
-    RelationshipKind, ports::ProjectAnalyzer,
+    RelationshipKind, normalize_cargo_package, ports::ProjectAnalyzer,
 };
 
 pub struct CargoWorkspaceAnalyzer;
@@ -97,7 +97,7 @@ impl ProjectAnalyzer for CargoWorkspaceAnalyzer {
                 .map_err(|e| DomainError::ConfigError(e.to_string()))?;
 
             for dep_name in member.dependencies.keys() {
-                let normalized = dep_name.replace('_', "-");
+                let normalized = normalize_cargo_package(dep_name);
                 if name_set.contains(&normalized)
                     && let Ok(rel) =
                         Relationship::new(package_name, &normalized, RelationshipKind::Composition)