feat: add trait impl support to TypedAST

- Added TypedTraitImpl struct for standalone impl blocks
- Added TypedImplAssociatedType for associated type definitions in impls
- Added Impl variant to TypedDeclaration enum
- Updated type_checker and multi_paradigm_checker to handle Impl

This enables parsing 'impl Trait for Type' blocks from ZynML stdlib.
TypeRegistry already has register_trait() and register_implementation()
methods, so the lowering infrastructure is ready.

Author: darmie

crates/typed_ast/src/multi_paradigm_checker.rs

@@ -405,6 +405,7 @@ impl TypeChecker {
             TypedDeclaration::TypeAlias(_)
             | TypedDeclaration::Class(_)
             | TypedDeclaration::Interface(_)
+            | TypedDeclaration::Impl(_)
             | TypedDeclaration::Enum(_)
             | TypedDeclaration::Module(_)
             | TypedDeclaration::Import(_)

crates/typed_ast/src/type_checker.rs

@@ -653,6 +653,7 @@ impl TypeChecker {
             // TODO: Implement other declaration types
             TypedDeclaration::Class(_)
             | TypedDeclaration::Interface(_)
+            | TypedDeclaration::Impl(_)
             | TypedDeclaration::Enum(_)
             | TypedDeclaration::TypeAlias(_)
             | TypedDeclaration::Module(_)

crates/typed_ast/src/typed_ast.rs

@@ -53,6 +53,7 @@ pub enum TypedDeclaration {
     Variable(TypedVariable),
     Class(TypedClass),
     Interface(TypedInterface),
+    Impl(TypedTraitImpl),
     Enum(TypedEnum),
     TypeAlias(TypedTypeAlias),
     Module(TypedModule),
@@ -1129,6 +1130,31 @@ pub struct TypedInterface {
     pub span: Span,
 }
 
+/// Trait implementation block
+/// Represents: impl TraitName<TypeArgs> for TypeName { ... }
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct TypedTraitImpl {
+    /// The trait being implemented (e.g., "Add" in "impl Add<T> for Vec<T>")
+    pub trait_name: InternedString,
+    /// Type arguments for the trait (e.g., <Tensor> in "impl Add<Tensor> for Tensor")
+    pub trait_type_args: Vec<Type>,
+    /// The type implementing the trait (e.g., "Tensor" in "impl Add for Tensor")
+    pub for_type: Type,
+    /// Method implementations
+    pub methods: Vec<TypedMethod>,
+    /// Associated type definitions (e.g., "type Output = Tensor")
+    pub associated_types: Vec<TypedImplAssociatedType>,
+    pub span: Span,
+}
+
+/// Associated type definition in impl block
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct TypedImplAssociatedType {
+    pub name: InternedString,
+    pub ty: Type,
+    pub span: Span,
+}
+
 /// Enum declaration
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct TypedEnum {