fix: feed Codex prompts through stdin

tests/test_gitea_service.py

@@ -18,8 +18,8 @@ def make_config(tmp_path: Path, **overrides: object) -> AppConfig:
         "scheduler": {"interval_seconds": 1, "concurrency": 1, "lease_seconds": 60},
         "workspace": {"root": tmp_path / "workspaces", "cleanup_on_success": False},
         "agents": {
-            "implementer": {"command": ["implementer", "{prompt_path}"]},
-            "reviewer": {"command": ["reviewer", "{prompt_path}"]},
+            "implementer": {"command": ["implementer", "-"]},
+            "reviewer": {"command": ["reviewer", "-"]},
         },
     }
     data.update(overrides)
@@ -144,8 +144,9 @@ class FakeRunner:
     def __init__(self, *, fail_role: str | None = None):
         self.fail_role = fail_role
 
-    def run(self, command, cwd):
+    def run(self, command, cwd, *, stdin=None):
         role = command[0]
+        assert stdin
         if role == self.fail_role:
             return AgentResult(exit_code=1, stdout="", stderr="failed")
         if role == "implementer":