Refuse to start with the state store or .env inside the clone

Answering "is the workspace where the agent runs, or what it works
on?" — it is what it works on, and conflating the two is dangerous
rather than merely untidy.

The agent commits its workspace with git add -A and pushes it, so
anything inside the clone reaches the project repository. A .env
placed there would publish the LiteLLM, Matrix and Gitea tokens as a
side effect of the agent working correctly: silently, once, and
probably unnoticed. Startup now refuses both that and a state store
inside the clone, and .env.example documents the intended layout.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nisse-dev/tests/test_config.py

@@ -89,3 +89,44 @@ def test_state_db_and_workspace_are_separate(tmp_path: Path) -> None:
     # A2: build artefacts must not share a volume with agent state.
     config = AgentConfig.from_env(COMPLETE)
     assert config.state_db.parent != config.workspace
+
+
+def test_state_db_inside_the_clone_is_refused(tmp_path: Path) -> None:
+    # git add -A would commit it, and the push would publish the agent's
+    # own state alongside the project.
+    work = tmp_path / "project"
+    with pytest.raises(ConfigError, match="inside the workspace"):
+        AgentConfig.from_env(
+            {
+                **COMPLETE,
+                "NISSE_WORKSPACE": str(work),
+                "NISSE_STATE_DB": str(work / "state.db"),
+            }
+        )
+
+
+def test_env_file_inside_the_clone_is_refused(tmp_path: Path) -> None:
+    # The severe case: the agent would commit and push its own credentials
+    # as a side effect of working correctly.
+    work = tmp_path / "project"
+    with pytest.raises(ConfigError, match="NISSE_ENV"):
+        AgentConfig.from_env(
+            {
+                **COMPLETE,
+                "NISSE_WORKSPACE": str(work),
+                "NISSE_STATE_DB": str(tmp_path / "state.db"),
+                "NISSE_ENV": str(work / ".env"),
+            }
+        )
+
+
+def test_sibling_paths_are_fine(tmp_path: Path) -> None:
+    config = AgentConfig.from_env(
+        {
+            **COMPLETE,
+            "NISSE_WORKSPACE": str(tmp_path / "project"),
+            "NISSE_STATE_DB": str(tmp_path / "state.db"),
+            "NISSE_ENV": str(tmp_path / ".env"),
+        }
+    )
+    assert config.workspace.name == "project"