wip: extend M5 ownership tests and cleanup emission

조건부 이동, 이중 destroy, 직접 drop 호출에 대한 실패 fixture를 추가하고
runtime harness와 test-dos.bat를 그에 맞춰 갱신한다.

M5는 아직 완료가 아니다. 모든 경로에서 정확히 1회 cleanup, defer/drop의 선언
역순 병합, try 전파 경로 cleanup, MaybeMoved 런타임 live flag, struct drop과
필드 역순 drop, 분기/루프 상태 합류, 누수/이중해제 카운터 harness가 남아 있다.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012PQm6oAvWX4Lp3iSN5AHGT

fec/tests/m5/bad-conditional.fe

@@ -0,0 +1,8 @@
+unit m5_bad_conditional;
+
+fn take(p: ^i32) -> void { mem.destroy(p); }
+
+fn bad(p: ^i32, flag: bool) -> void {
+    if flag { take(p); }
+    p.^ = 3;
+}

fec/tests/m5/bad-double.fe

@@ -0,0 +1,6 @@
+unit m5_bad_double;
+
+fn bad(p: ^i32) -> void {
+    mem.destroy(p);
+    mem.destroy(p);
+}

fec/tests/m5/bad-drop.fe

@@ -0,0 +1,11 @@
+unit m5_bad_drop;
+
+struct Box {
+    value: i32,
+    fn drop(self: &mut Self) { self.value = 0; }
+}
+
+fn bad() -> void {
+    var b: Box = Box{ value: 1 };
+    b.drop();
+}

fec/tests/m5/runtime.c

@@ -1,9 +1,52 @@
+#include <stdlib.h>
+#include <stddef.h>
+
+#undef malloc
+#undef free
+
 extern long fe_m5_runtime_run(long mode);
+extern void fe_m5_runtime_conditional(unsigned char flag);
+extern void fe_m5_runtime_argument_cleanup(void);
+
+static void *live_ptrs[64];
+static unsigned live_count;
+static unsigned alloc_count;
+static unsigned free_count;
+static unsigned double_free_count;
+
+void *m5_malloc(size_t size)
+{
+    void *p = malloc(size);
+    if (p && live_count < 64) live_ptrs[live_count++] = p;
+    if (p) ++alloc_count;
+    return p;
+}
+
+void m5_free(void *p)
+{
+    unsigned i;
+    if (!p) return;
+    for (i = 0; i < live_count; ++i) {
+        if (live_ptrs[i] == p) {
+            live_ptrs[i] = live_ptrs[--live_count];
+            ++free_count;
+            free(p);
+            return;
+        }
+    }
+    ++double_free_count;
+}
 
 int main(void)
 {
     if (fe_m5_runtime_run(0) != 0) return 1;
     if (fe_m5_runtime_run(1) != 9) return 2;
     if (fe_m5_runtime_run(2) != 0) return 3;
+    fe_m5_runtime_conditional(0);
+    fe_m5_runtime_conditional(1);
+    fe_m5_runtime_argument_cleanup();
+    if (double_free_count != 0) return 4;
+    if (live_count != 0) return 5;
+    if (alloc_count != free_count) return 6;
     return 0;
 }

fec/tests/m5/runtime.fe

@@ -1,5 +1,7 @@
 unit m5_runtime;
 
+fn take(p: ^i32) -> void { mem.destroy(p); }
+
 pub fn run(mode: i32) -> i32 {
     var p: ^i32 = try mem.create(i32);
     defer { mem.destroy(p); }
@@ -9,11 +11,17 @@ pub fn run(mode: i32) -> i32 {
         p.^ = 9;
         return p.^;
     }
-    while true {
-        break;
-    }
-    if mode == 2 {
-        return 0;
-    }
+    while true { break; }
+    if mode == 2 { return 0; }
     return p.^ - 7;
 }
+
+pub fn conditional(flag: bool) -> void {
+    var p: ^i32 = try mem.create(i32);
+    if flag { take(p); }
+}
+
+pub fn argument_cleanup() -> void {
+    let p: ^i32 = try mem.create(i32);
+    take(p);
+}