feat(settings): add explicit settings dir override for sandboxed runs

Add LORA_MANAGER_SETTINGS_DIR env var and standalone --settings-path to pin
the settings location (settings.json, cache/, wildcards/, backups/, logs/,
stats/) to an arbitrary directory. The override takes precedence over
portable mode and the platform user config dir, and skips legacy migration,
so sandboxed dev/E2E runs no longer need to write settings.json in the repo
root or collide with the real instance.

standalone.py pre-scans argv for --settings-path at import time because the
settings location is resolved before main() parses arguments. SettingsManager
portable-switch migration is a no-op while the directory is pinned.

Update the lora-manager-e2e skill (prefer --settings-path sandboxing;
start_server.py passes it through) and the lora-manager-runtime-context
skill (document precedence; inspect script honors the override).

tests/utils/test_settings_paths.py

@@ -6,7 +6,26 @@ import os
 
 import pytest
 
-from py.utils.settings_paths import _should_use_portable_settings
+from py.utils.settings_paths import (
+    SETTINGS_DIR_ENV,
+    _should_use_portable_settings,
+    ensure_settings_file,
+    get_settings_dir,
+    get_settings_dir_override,
+    is_settings_dir_pinned,
+    set_settings_dir_override,
+)
+
+
+def _redirect_paths(tmp_path, monkeypatch):
+    """Pin project root and user config dir resolution to temp paths."""
+    monkeypatch.setattr(
+        "py.utils.settings_paths.get_project_root", lambda: str(tmp_path / "repo")
+    )
+    monkeypatch.setattr(
+        "py.utils.settings_paths.user_config_dir",
+        lambda *args, **kwargs: str(tmp_path / "user_config"),
+    )
 
 
 class TestShouldUsePortableSettings:
@@ -54,3 +73,69 @@ class TestShouldUsePortableSettings:
             mp.setenv("LORA_MANAGER_PORTABLE", "1")
             result = _should_use_portable_settings(str(missing), logging.getLogger())
             assert result is True
+
+
+class TestExplicitSettingsDirOverride:
+    """Tests for the LORA_MANAGER_SETTINGS_DIR / --settings-path override."""
+
+    def test_env_override_wins_over_portable_and_user_config(self, tmp_path, monkeypatch):
+        _redirect_paths(tmp_path, monkeypatch)
+        repo = tmp_path / "repo"
+        repo.mkdir()
+        (repo / "settings.json").write_text(
+            json.dumps({"use_portable_settings": True}), encoding="utf-8"
+        )
+        custom_dir = tmp_path / "custom" / "e2e"
+
+        monkeypatch.setenv(SETTINGS_DIR_ENV, str(custom_dir))
+        monkeypatch.delenv("LORA_MANAGER_PORTABLE", raising=False)
+
+        assert is_settings_dir_pinned()
+        target = get_settings_dir(create=True)
+        assert target == str(custom_dir.resolve())
+        assert target == os.path.abspath(str(custom_dir))
+        assert custom_dir.is_dir()
+
+        # The override is independent of the effective use_portable flag.
+        with pytest.MonkeyPatch.context() as mp:
+            mp.setenv("LORA_MANAGER_PORTABLE", "1")
+            assert get_settings_dir(create=False) == os.path.abspath(str(custom_dir))
+
+    def test_env_override_normalizes_tilde(self, monkeypatch):
+        monkeypatch.setenv(SETTINGS_DIR_ENV, "~/lm-e2e-settings")
+        override = get_settings_dir_override()
+        assert override == os.path.abspath(os.path.expanduser("~/lm-e2e-settings"))
+
+    def test_ensure_settings_file_pins_path_and_skips_migration(self, tmp_path, monkeypatch):
+        _redirect_paths(tmp_path, monkeypatch)
+        repo = tmp_path / "repo"
+        repo.mkdir()
+        legacy = repo / "settings.json"
+        legacy.write_text(json.dumps({"language": "ja"}), encoding="utf-8")
+        custom_dir = tmp_path / "custom"
+
+        monkeypatch.setenv(SETTINGS_DIR_ENV, str(custom_dir))
+
+        settings_file = ensure_settings_file()
+        assert settings_file == os.path.join(os.path.abspath(str(custom_dir)), "settings.json")
+        assert os.path.isdir(str(custom_dir))
+        # The legacy (project-root) file must NOT be migrated into the custom dir.
+        assert legacy.exists()
+        assert not (custom_dir / "settings.json").exists()
+        assert not (tmp_path / "user_config" / "settings.json").exists()
+
+    def test_programmatic_override_and_clear(self, tmp_path, monkeypatch):
+        _redirect_paths(tmp_path, monkeypatch)
+        monkeypatch.delenv(SETTINGS_DIR_ENV, raising=False)
+
+        custom_dir = tmp_path / "prog"
+        previous = set_settings_dir_override(str(custom_dir))
+        assert previous is None
+        assert is_settings_dir_pinned()
+        assert get_settings_dir(create=False) == os.path.abspath(str(custom_dir))
+
+        previous = set_settings_dir_override(None)
+        assert previous == os.path.abspath(str(custom_dir))
+        assert not is_settings_dir_pinned()
+        # Falls back to the (redirected) platform user config dir.
+        assert get_settings_dir(create=False) == str(tmp_path / "user_config")