feat(joinir): emit balanced depth-scan derived vars

src/mir/join_ir/normalized/fixtures.rs

@@ -137,6 +137,7 @@ pub fn build_pattern2_minimal_structured() -> JoinModule {
             skeleton: None, // Phase 92 P0-3: skeleton=None for backward compatibility
             condition_only_recipe: None, // Phase 93 P0: None for normal loops
             body_local_derived_recipe: None, // Phase 94: None for fixture
+            balanced_depth_scan_recipe: None, // Phase 107: None for fixture
         },
     )
     .expect("pattern2 minimal lowering should succeed");