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/opt/mir_aot_prep.hako

@@ -41,14 +41,14 @@ static box AotPrepBox {
     local k1 = "\"value\":{\"type\":\"i64\",\"value\":"
     local a_pos = body.indexOf(k1, p0)
     if a_pos < 0 { return "" }
-    a_pos = a_pos + k1.size()
+    a_pos = a_pos + k1.length()
     local a_s = JsonCursorBox.digits_from(body, a_pos)
     if a_s == null || a_s == "" { return "" }
     local p1 = body.indexOf("\"op\":\"const\"", a_pos)
     if p1 < 0 { return "" }
     local b_pos = body.indexOf(k1, p1)
     if b_pos < 0 { return "" }
-    b_pos = b_pos + k1.size()
+    b_pos = b_pos + k1.length()
     local b_s = JsonCursorBox.digits_from(body, b_pos)
     if b_s == null || b_s == "" { return "" }
     // operation symbol
@@ -69,15 +69,15 @@ static box AotPrepBox {
     // Build folded instruction array: [const rv -> dst:1, ret 1]
     local folded = "[{\"op\":\"const\",\"dst\":1,\"value\":{\"type\":\"i64\",\"value\":" + (""+rv) + "}},{\"op\":\"ret\",\"value\":1}]"
     // Splice back into whole JSON and return
-    return json.substring(0, start+1) + folded + json.substring(end, json.size())
+    return json.substring(0, start+1) + folded + json.substring(end, json.length())
   }
 
   _to_i64(s) {
     // crude but sufficient for our immediate range
     local i = 0; local neg = 0
-    if s.size() > 0 && s.substring(0,1) == "-" { neg = 1; i = 1 }
+    if s.length() > 0 && s.substring(0,1) == "-" { neg = 1; i = 1 }
     local out = 0
-    loop (i < s.size()) {
+    loop (i < s.length()) {
       local ch = s.substring(i, i+1)
       if ch < "0" || ch > "9" { break }
       out = out * 10 + (ch - "0")
@@ -99,7 +99,7 @@ static box AotPrepBox {
       local p = json.indexOf(pat, i)
       if p < 0 { break }
       // Parse dst number
-      local pnum = p + pat.size()
+      local pnum = p + pat.length()
       local digits = JsonCursorBox.digits_from(json, pnum)
       if digits == null || digits == "" { i = p + 1; continue }
       local dst_s = digits
@@ -114,7 +114,7 @@ static box AotPrepBox {
       local obj_end = me._seek_object_end(json, obj_start)
       if obj_end < 0 { i = p + 1; continue }
       // Validate dst is unused after this object
-      local tail = json.substring(obj_end+1, json.size())
+      local tail = json.substring(obj_end+1, json.length())
       // Search common reference patterns: ":<dst>" after a key
       local ref = ":" + dst_s
       if tail.indexOf(ref) >= 0 {
@@ -124,11 +124,11 @@ static box AotPrepBox {
       local cut_left = obj_start
       local cut_right = obj_end + 1
       // Trim a single trailing comma to keep JSON valid in arrays
-      if cut_right < json.size() {
+      if cut_right < json.length() {
         local ch = json.substring(cut_right, cut_right+1)
         if ch == "," { cut_right = cut_right + 1 }
       }
-      json = json.substring(0, cut_left) + json.substring(cut_right, json.size())
+      json = json.substring(0, cut_left) + json.substring(cut_right, json.length())
       changed = 1
       i = cut_left
     }
@@ -140,13 +140,13 @@ static box AotPrepBox {
   // Handles nested objects and string literals with escapes.
   _seek_object_end(s, start) {
     if s == null { return -1 }
-    if start < 0 || start >= s.size() { return -1 }
+    if start < 0 || start >= s.length() { return -1 }
     if s.substring(start, start+1) != "{" { return -1 }
     local i = start
     local depth = 0
     local in_str = 0
     local esc = 0
-    loop (i < s.size()) {
+    loop (i < s.length()) {
       local ch = s.substring(i, i+1)
       if in_str == 1 {
         if esc == 1 { esc = 0 }