步骤D：用例 22_multi_instance（FB 共享体多实例隔离，a=102/204/306）+ 全量回归

tests/src/cases_test.cpp

@@ -66,6 +66,7 @@ namespace {
         {"19_recursive_call", Outcome::CompileError, "recursive call"},
         {"20_line1", Outcome::Ok, ""},
         {"21_var_temp", Outcome::Ok, ""},
+        {"22_multi_instance", Outcome::Ok, ""},
     };
 
     bool run_case(const char* dir, Outcome want, const char* keyword) {

tests/src/compiler_test.cpp

@@ -202,7 +202,7 @@ static bool test_all_cases() {
         }
         ++n;
     }
-    CHECK(n == 21);
+    CHECK(n == 22);
     return true;
 }
 

tests/src/vm_test.cpp

@@ -374,6 +374,15 @@ static bool test_cases_positive() {
     CHECK(m.run_cycle() == vm::Fault::None);
     CHECK(slot(m, 0) == 10109);
 
+    // 22 多实例共享体：Counter 单函数服务 c1/c2，a = 102/204/306
+    CHECK(make_machine("tests/cases/22_multi_instance", &m, &err));
+    m.run_cycle();
+    CHECK(slot(m, 0) == 102);
+    m.run_cycle();
+    CHECK(slot(m, 0) == 204);
+    CHECK(m.run_cycle() == vm::Fault::None);
+    CHECK(slot(m, 0) == 306);
+
     // 20 line1：I 组合 → Q0_0 真值表（槽 0=急停 1=I0_0 2=I0_1 3=Q0_0）
     CHECK(make_machine("tests/cases/20_line1", &m, &err));
     struct {