test(phase1): add unit tests for telemetry, plugin, rag, persistence

Add initial unit tests for Phase 1 of test coverage improvement:
- telemetry: test initialization, payload sanitization, early returns (14.3% → 62.9%)
- plugin: test _parse_plugin_id static method
- rag: test _to_i18n_name static method
- persistence: test serialize_model with datetime handling

Overall core coverage: 41.9% → 42.2%

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/unit_tests/rag/test_i18n_conversion.py

@@ -0,0 +1,64 @@
+"""Unit tests for RAG i18n name conversion.
+
+Tests cover:
+- _to_i18n_name() static method
+"""
+from __future__ import annotations
+
+import pytest
+from importlib import import_module
+
+
+def get_kbmgr_module():
+    """Lazy import to avoid circular import issues."""
+    return import_module('langbot.pkg.rag.knowledge.kbmgr')
+
+
+class TestToI18nName:
+    """Tests for _to_i18n_name static method."""
+
+    def test_string_input_wrapped(self):
+        """Test that string input is wrapped into i18n dict."""
+        kbmgr = get_kbmgr_module()
+        result = kbmgr.RAGManager._to_i18n_name('Test Engine')
+        assert result == {'en_US': 'Test Engine', 'zh_Hans': 'Test Engine'}
+
+    def test_dict_input_preserved(self):
+        """Test that dict input is returned as-is."""
+        kbmgr = get_kbmgr_module()
+        input_dict = {'en_US': 'English Name', 'zh_Hans': '中文名', 'ja_JP': '日本語名'}
+        result = kbmgr.RAGManager._to_i18n_name(input_dict)
+        assert result == input_dict
+        assert result is input_dict  # Should return the same object
+
+    def test_empty_string_handling(self):
+        """Test that empty string is handled correctly."""
+        kbmgr = get_kbmgr_module()
+        result = kbmgr.RAGManager._to_i18n_name('')
+        assert result == {'en_US': '', 'zh_Hans': ''}
+
+    def test_none_input_handling(self):
+        """Test that None is converted to string 'None'."""
+        kbmgr = get_kbmgr_module()
+        result = kbmgr.RAGManager._to_i18n_name(None)
+        assert result == {'en_US': 'None', 'zh_Hans': 'None'}
+
+    def test_number_input_converted_to_string(self):
+        """Test that numbers are converted to strings."""
+        kbmgr = get_kbmgr_module()
+        result = kbmgr.RAGManager._to_i18n_name(123)
+        assert result == {'en_US': '123', 'zh_Hans': '123'}
+
+    def test_dict_with_partial_keys_preserved(self):
+        """Test that dict with only some i18n keys is preserved."""
+        kbmgr = get_kbmgr_module()
+        input_dict = {'en_US': 'Only English'}
+        result = kbmgr.RAGManager._to_i18n_name(input_dict)
+        assert result == {'en_US': 'Only English'}
+
+    def test_dict_with_extra_keys_preserved(self):
+        """Test that dict with extra non-i18n keys is preserved."""
+        kbmgr = get_kbmgr_module()
+        input_dict = {'en_US': 'English', 'extra_key': 'extra_value'}
+        result = kbmgr.RAGManager._to_i18n_name(input_dict)
+        assert result == {'en_US': 'English', 'extra_key': 'extra_value'}