Этап 1: трей, окно чата и текстовый диалог с LLM

- PySide6: значок в трее с индикацией состояния, окно чата со стримингом и markdown
- Единый OpenAI-совместимый клиент (Ollama, LM Studio, OpenRouter)
- config.yaml с автосозданием, слиянием с умолчаниями и подстановкой ${ENV}
- Тесты конфига и сборки сообщений

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

tests/test_config.py

@@ -0,0 +1,62 @@
+from pathlib import Path
+
+import pytest
+
+from agr_assistent.config import ConfigError, load_config
+
+
+def _write(path: Path, text: str) -> Path:
+    path.write_text(text, encoding="utf-8")
+    return path
+
+
+def test_creates_default_config_when_missing(tmp_path: Path) -> None:
+    path = tmp_path / "config.yaml"
+
+    config = load_config(path)
+
+    assert path.exists()
+    assert config.llm.provider == "ollama"
+    assert config.llm.active_provider.base_url == "http://localhost:11434/v1"
+
+
+def test_user_values_override_defaults(tmp_path: Path) -> None:
+    path = _write(
+        tmp_path / "config.yaml",
+        "llm:\n  provider: openrouter\n  providers:\n    openrouter:\n      model: my/model\n",
+    )
+
+    config = load_config(path)
+
+    assert config.llm.active_provider.model == "my/model"
+    assert config.llm.active_provider.base_url == "https://openrouter.ai/api/v1"
+    assert config.llm.temperature == 0.7
+
+
+def test_api_key_expands_environment_variable(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    path = _write(
+        tmp_path / "config.yaml",
+        "llm:\n  providers:\n    openrouter:\n      api_key: ${TEST_AGR_KEY}\n",
+    )
+
+    monkeypatch.setenv("TEST_AGR_KEY", "secret")
+    assert load_config(path).llm.providers["openrouter"].api_key == "secret"
+
+    monkeypatch.delenv("TEST_AGR_KEY")
+    assert load_config(path).llm.providers["openrouter"].api_key == ""
+
+
+def test_unknown_provider_is_rejected(tmp_path: Path) -> None:
+    path = _write(tmp_path / "config.yaml", "llm:\n  provider: nope\n")
+
+    with pytest.raises(ConfigError, match="nope"):
+        load_config(path)
+
+
+def test_invalid_yaml_is_rejected(tmp_path: Path) -> None:
+    path = _write(tmp_path / "config.yaml", "llm: [unclosed\n")
+
+    with pytest.raises(ConfigError):
+        load_config(path)