Refactor: Remove explicit upvalue analysis pass

The `UpvalueAnalyzer` pass is no longer necessary as the binder now
directly tracks captures. This commit removes the `UpvalueAnalyzer`
struct and associated logic from `src/ast/compiler/upvalues.rs`.

The `Binder::bind_root` function now returns the `captures` map, which
is then processed by a new `CapturePass` in `src/ast/environment.rs`
before type checking. This consolidates capture logic within the binder
and its subsequent processing steps.

src/ast/environment.rs

@@ -17,10 +17,12 @@ use crate::ast::compiler::specializer::{FunctionRegistry, MonoCache, Specializer
 use crate::ast::compiler::tco::{ExecNode, TCO};
 use crate::ast::rtl;
 use crate::ast::rtl::intrinsics;
-use crate::ast::types::{Object, Purity, StaticType, Value};
+use crate::ast::types::{
+    Identity, NodeIdentity, Object, Purity, SourceLocation, StaticType, Value,
+};
 
 pub struct Environment {
-    pub global_names: Rc<RefCell<HashMap<Symbol, u32>>>,
+    pub global_names: Rc<RefCell<HashMap<Symbol, (u32, Identity)>>>,
     pub global_types: Rc<RefCell<HashMap<u32, StaticType>>>,
     pub global_purity: Rc<RefCell<HashMap<u32, Purity>>>,
     pub global_values: Rc<RefCell<Vec<Value>>>,
@@ -55,7 +57,7 @@ impl FunctionRegistry for EnvFunctionRegistry {
 }
 
 struct RuntimeMacroEvaluator {
-    global_names: Rc<RefCell<HashMap<Symbol, u32>>>,
+    global_names: Rc<RefCell<HashMap<Symbol, (u32, Identity)>>>,
     global_types: Rc<RefCell<HashMap<u32, StaticType>>>,
     global_values: Rc<RefCell<Vec<Value>>>,
 }
@@ -72,7 +74,8 @@ impl MacroEvaluator for RuntimeMacroEvaluator {
             return Ok(Value::Object(Rc::new(arg_node.clone()) as Rc<dyn Object>));
         }
 
-        let bound_ast = Binder::bind_root(self.global_names.clone(), node)?;
+        let (bound_ast, captures) = Binder::bind_root(self.global_names.clone(), node)?;
+        let bound_ast = crate::ast::compiler::captures::CapturePass::apply(bound_ast, &captures);
         let checker = TypeChecker::new(self.global_types.clone());
         let typed_ast = checker.check(bound_ast, &[])?;
         let exec_ast = TCO::optimize(Analyzer::analyze(&typed_ast, &HashMap::new())); // Minimal analysis for macro eval
@@ -131,7 +134,10 @@ impl Environment {
         let mut purity = self.global_purity.borrow_mut();
 
         let idx = values.len() as u32;
-        names.insert(Symbol::from(name), idx);
+        let identity = Rc::new(NodeIdentity {
+            location: SourceLocation { line: 0, col: 0 },
+        });
+        names.insert(Symbol::from(name), (idx, identity));
         types.insert(idx, ty);
         purity.insert(idx, func.purity);
         values.push(Value::Function(func));
@@ -161,7 +167,10 @@ impl Environment {
         let mut purity = self.global_purity.borrow_mut();
 
         let idx = values.len() as u32;
-        names.insert(Symbol::from(name), idx);
+        let identity = Rc::new(NodeIdentity {
+            location: SourceLocation { line: 0, col: 0 },
+        });
+        names.insert(Symbol::from(name), (idx, identity));
         types.insert(idx, ty);
         purity.insert(idx, Purity::Pure);
         values.push(val);
@@ -186,7 +195,9 @@ impl Environment {
         }
 
         let expanded_ast = self.get_expander().expand(untyped_ast)?;
-        let bound_ast = Binder::bind_root(self.global_names.clone(), &expanded_ast)?;
+        let (bound_ast, captures) = Binder::bind_root(self.global_names.clone(), &expanded_ast)?;
+        let bound_ast = crate::ast::compiler::captures::CapturePass::apply(bound_ast, &captures);
+
         LambdaCollector::collect(&bound_ast, &mut self.function_registry.borrow_mut());
 
         let checker = TypeChecker::new(self.global_types.clone());