fix(compiler): 重写闭包捕获分析为 AST 级，修复 MAKE_CELL 时序

crates/oxide_compiler/src/expr/assignment.rs

@@ -146,7 +146,7 @@ impl Compiler {
                     return Ok(val_reg);
                 }
                 // Check if target is a captured cell
-                if ctx.scopes.symbols.lookup_is_captured(name) {
+                if ctx.captured_bindings.contains(name) {
                     let cell_idx = ctx
                         .scopes
                         .cell_registry

crates/oxide_compiler/src/expr/identifier.rs

@@ -18,7 +18,7 @@ impl Compiler {
             }
         }
 
-        if ctx.scopes.symbols.lookup_is_captured(name) {
+        if ctx.captured_bindings.contains(name) {
             let cell_idx = ctx
                 .scopes
                 .cell_registry

crates/oxide_compiler/src/expr/operator/mod.rs

@@ -222,7 +222,7 @@ impl Compiler {
                 let name = id.name.as_str();
                 // Check if this is an upvalue or captured cell reference
                 let uv_idx = ctx.current_upvalue_captures.iter().position(|u| u.name == name);
-                let is_captured = ctx.scopes.symbols.lookup_is_captured(name);
+                let is_captured = ctx.captured_bindings.contains(name);
                 if let Some(uv) = uv_idx {
                     // Upvalue: LOAD_UPVALUE + CONST(1) + ADD/SUB + STORE_UPVALUE
                     let val_reg = ctx.alloc_reg();