fix: decode harness git output as utf-8

scripts/execute.py

@@ -58,7 +58,7 @@ class StepExecutor:
     """Phase 디렉토리 안의 step들을 순차 실행하는 하네스."""
 
     MAX_RETRIES = 3
-    FEAT_MSG = "feat({phase}): step {num} — {name}"
+    FEAT_MSG = "feat({phase}): step {num} - {name}"
     CHORE_MSG = "chore({phase}): step {num} output"
     TZ = timezone(timedelta(hours=9))
 
@@ -112,7 +112,9 @@ class StepExecutor:
 
     def _run_git(self, *args) -> subprocess.CompletedProcess:
         cmd = ["git"] + list(args)
-        return subprocess.run(cmd, cwd=self._root, capture_output=True, text=True)
+        return subprocess.run(
+            cmd, cwd=self._root, capture_output=True, text=True, encoding="utf-8"
+        )
 
     def _checkout_branch(self):
         branch = f"feat-{self._phase_name}"