fix(mir/builder): clear metadata maps to prevent type pollution between static boxes

Root cause: When compiling multiple static boxes, metadata from using statements
and previous box compilations (variable_map, value_origin_newbox, value_types)
leaked into subsequent compilations, causing parameters to be incorrectly typed.
For example, "args" parameter was incorrectly inferred as "ParserBox" instead of
its actual type.

Changes:
1. lifecycle.rs:95-97: Clear metadata before compiling each non-Main static box
2. decls.rs:42-44: Clear metadata before Phase 1 compilation in build_static_main_box
3. exprs.rs:170-172: Clear metadata before processing static box methods
4. builder_calls.rs:164-178: Add debug traces for value_origin_newbox/value_types

Impact:
- Fixes StageBArgsBox.resolve_src ValueId(21) undefined error
- Prevents "ParserBox" type contamination of parameters
- Ensures clean compilation context for each static box

Note: Revealed new bug in StageBBodyExtractorBox (Copy from undefined ValueId(114))
which needs separate investigation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/mir/builder/lifecycle.rs

@@ -87,6 +87,14 @@ impl super::MirBuilder {
                             if name == "Main" {
                                 main_static = Some((name.clone(), methods.clone()));
                             } else {
+                                // ✅ CRITICAL FIX: Clear metadata maps BEFORE compiling each static box
+                                // This prevents pollution from using statement resolution and previous boxes
+                                // from leaking into this box's method compilations.
+                                // Root cause: Using statements and previous box compilations create metadata
+                                // (variable_map, value_origin_newbox, value_types) that leaks into subsequent compilations.
+                                self.variable_map.clear();
+                                self.value_origin_newbox.clear();
+                                self.value_types.clear();
                                 // Lower all static methods into standalone functions: BoxName.method/Arity
                                 for (mname, mast) in methods.iter() {
                                     if let N::FunctionDeclaration { params, body, .. } = mast {