fix(mir): PHI検証panic修正 - update_cfg()を検証前に呼び出し

A案実装: debug_verify_phi_inputs呼び出し前にCFG predecessorを更新

修正箇所（7箇所）:
- src/mir/builder/phi.rs:50, 73, 132, 143
- src/mir/builder/ops.rs:273, 328, 351

根本原因:
- Branch/Jump命令でsuccessorは即座に更新
- predecessorはupdate_cfg()で遅延再構築
- PHI検証が先に実行されてpredecessor未更新でpanic

解決策:
- 各debug_verify_phi_inputs呼び出し前に
  if let Some(func) = self.current_function.as_mut() {
      func.update_cfg();
  }
  を挿入してCFGを同期

影響: if/else文、論理演算子(&&/||)のPHI生成が正常動作

lang/src/shared/json/json_utils.hako

@@ -10,7 +10,7 @@ static box JsonUtilsBox {
     local pattern = "\"" + key + "\""
     local idx = StringHelpers.index_of(json, 0, pattern)
     if idx < 0 { return null }
-    idx = idx + pattern.size()
+    idx = idx + pattern.length()
     idx = StringHelpers.skip_ws(json, idx)
     if json.substring(idx, idx + 1) != ":" { return null }
     idx = StringHelpers.skip_ws(json, idx + 1)
@@ -25,15 +25,15 @@ static box JsonUtilsBox {
     local raw = me.extract_value(json, key)
     if raw == null { return default_value }
     local trimmed = StringHelpers.trim(raw)
-    if trimmed.size() >= 2 && trimmed.substring(0,1) == "\"" && trimmed.substring(trimmed.size()-1, trimmed.size()) == "\"" {
-      return me.unescape_string(trimmed.substring(1, trimmed.size()-1))
+    if trimmed.length() >= 2 && trimmed.substring(0,1) == "\"" && trimmed.substring(trimmed.length()-1, trimmed.length()) == "\"" {
+      return me.unescape_string(trimmed.substring(1, trimmed.length()-1))
     }
     return default_value
   }
 
   // Read JSON value (dispatch to appropriate reader)
   read_value(json, idx) {
-    local n = json.size()
+    local n = json.length()
     if idx >= n { return "@" + StringHelpers.int_to_str(idx) }
     local ch = json.substring(idx, idx + 1)
     if ch == "\"" { return me.read_string(json, idx) }
@@ -45,7 +45,7 @@ static box JsonUtilsBox {
   // Read JSON string (escape-aware) with position marker
   read_string(json, idx) {
     local i = idx + 1
-    local n = json.size()
+    local n = json.length()
     local done = 0
     loop(done == 0 && i < n) {
       local ch = json.substring(i, i + 1)
@@ -61,7 +61,7 @@ static box JsonUtilsBox {
   // Skip JSON string (returns end position)
   skip_string(json, idx) {
     local i = idx + 1
-    local n = json.size()
+    local n = json.length()
     local done = 0
     loop(done == 0 && i < n) {
       local ch = json.substring(i, i + 1)
@@ -75,7 +75,7 @@ static box JsonUtilsBox {
   read_object(json, idx) {
     local depth = 0
     local i = idx
-    local n = json.size()
+    local n = json.length()
     loop(i < n) {
       local ch = json.substring(i, i + 1)
       if ch == "\"" {
@@ -96,7 +96,7 @@ static box JsonUtilsBox {
   read_array(json, idx) {
     local depth = 0
     local i = idx
-    local n = json.size()
+    local n = json.length()
     loop(i < n) {
       local ch = json.substring(i, i + 1)
       if ch == "\"" {
@@ -115,7 +115,7 @@ static box JsonUtilsBox {
 
   // Read JSON literal (number/true/false/null) with position marker
   read_literal(json, idx) {
-    local n = json.size()
+    local n = json.length()
     local i = idx
     loop(i < n) {
       local ch = json.substring(i, i + 1)
@@ -128,7 +128,7 @@ static box JsonUtilsBox {
   // Split JSON array at top-level commas (depth-aware, escape-aware)
   split_top_level(array_json) {
     local out = new ArrayBox()
-    local n = array_json.size()
+    local n = array_json.length()
     local i = 1
     local start = 1
     local depth = 0
@@ -169,7 +169,7 @@ static box JsonUtilsBox {
     if s == null { return "" }
     local out = ""
     local i = 0
-    local n = s.size()
+    local n = s.length()
     loop(i < n) {
       local ch = s.substring(i, i + 1)
       if ch == "\\" && i + 1 < n {