simplify: port CondBranch const-fold + CIntToCBool to C (chunks 5-6)

Two more Category 2 handlers using SimplifyEnv:
- simplify_cint_to_cbool_c: folds known int to CBool constant
- simplify_cond_branch_const_c: folds CondBranch with known-constant
  condition to unconditional Branch (falls through to C++ for
  IntConvert forwarding path)
Adds make_cbool_type helper for CBool HirType construction.

Author: SonicField

Python/jit/hir/simplify.cpp

@@ -2749,8 +2749,13 @@ Register* simplifyInstr(Env& env, const Instr* instr) {
     case Opcode::kCompare:
       return simplifyCompare(env, static_cast<const Compare*>(instr));
 
-    case Opcode::kCondBranch:
+    case Opcode::kCondBranch: {
+      SimplifyEnv cenv = make_c_env();
+      auto *r = static_cast<Register*>(simplify_cond_branch_const_c(&cenv, instr));
+      sync_c_env(cenv);
+      if (r) return r;
       return simplifyCondBranch(env, instr);
+    }
     case Opcode::kCondBranchCheckType:
       return simplifyCondBranchCheckType(
           env, static_cast<const CondBranchCheckType*>(instr));

Python/jit/hir/simplify_c.c

@@ -89,6 +89,21 @@ void *simplify_cint_to_cbool_c(SimplifyEnv *env, const void *instr) {
     return NULL;
 }
 
+/* ---- simplifyCondBranch (partial — constant condition folding) ----
+ * If condition is a known int constant, fold to unconditional Branch. */
+void *simplify_cond_branch_const_c(SimplifyEnv *env, const void *instr) {
+    void *cond = hir_c_get_operand(instr, 0);
+    HirType cond_type = hir_register_type(cond);
+    if (hir_type_has_int_spec(&cond_type)) {
+        intptr_t spec = hir_type_int_spec(&cond_type);
+        void *target = hir_c_successor(instr, spec ? 0 : 1);
+        extern void *hir_c_create_branch_cpp(void *target_block);
+        void *branch = hir_c_create_branch_cpp(target);
+        return simplify_env_emit(env, branch);
+    }
+    return NULL;
+}
+
 /* ---- simplifyPrimitiveBoxBool ----
  * If input is a known int constant, replace with Py_True/Py_False. */
 void *simplify_primitive_box_bool_c(SimplifyEnv *env, const void *instr) {

Python/jit/hir/simplify_c.h

@@ -33,6 +33,7 @@ void *simplify_guard_type_identity_c(const void *instr);
 /* Env-using handlers (Category 2) */
 void *simplify_primitive_box_bool_c(SimplifyEnv *env, const void *instr);
 void *simplify_cint_to_cbool_c(SimplifyEnv *env, const void *instr);
+void *simplify_cond_branch_const_c(SimplifyEnv *env, const void *instr);
 
 #ifdef __cplusplus
 }