feat: add avatar metrics tracking feature (#111)

* feat: add avatar metrics tracking feature (#110)

Add AvatarMetrics dataclass for tracking avatar state snapshots

- Add AvatarMetrics dataclass for recording monthly snapshots
- Add metrics_history field to Avatar with opt-in tracking
- Implement automatic monthly snapshot recording in Simulator
- Add backward compatibility support for existing save files
- Set default tracking limit to 1200 months (100 years)
- Add comprehensive tests with 100% coverage
- Move documentation to specs directory with simplified chinese

* fix: convert Traditional Chinese comments to Simplified Chinese

修正程式碼中的繁體中文註解為簡體中文，以符合專案規範。

Fix Traditional Chinese comments to Simplified Chinese in codebase.

tests/test_avatar_metrics.py

@@ -0,0 +1,146 @@
+"""
+测试 Avatar 状态追踪功能
+"""
+import pytest
+from src.classes.avatar_metrics import AvatarMetrics, MetricTag
+from src.classes.calendar import MonthStamp
+
+
+def test_avatar_metrics_creation():
+    """测试状态快照创建"""
+    metrics = AvatarMetrics(
+        timestamp=MonthStamp(100),
+        age=20,
+        cultivation_level=5,
+        cultivation_progress=100,
+        hp=100.0,
+        hp_max=100.0,
+        spirit_stones=50,
+        relations_count=3,
+        known_regions_count=2,
+        tags=["breakthrough"],
+    )
+
+    assert metrics.age == 20
+    assert metrics.cultivation_level == 5
+    assert metrics.cultivation_progress == 100
+    assert metrics.hp == 100.0
+    assert metrics.hp_max == 100.0
+    assert metrics.spirit_stones == 50
+    assert metrics.relations_count == 3
+    assert metrics.known_regions_count == 2
+    assert "breakthrough" in metrics.tags
+    assert metrics.timestamp == MonthStamp(100)
+
+
+def test_avatar_metrics_serialization():
+    """测试序列化与反序列化"""
+    original = AvatarMetrics(
+        timestamp=MonthStamp(200),
+        age=30,
+        cultivation_level=10,
+        cultivation_progress=500,
+        hp=150.0,
+        hp_max=200.0,
+        spirit_stones=1000,
+        relations_count=5,
+        known_regions_count=10,
+        tags=["injured", "battle"],
+    )
+
+    # 序列化
+    data = original.to_save_dict()
+    assert isinstance(data, dict)
+    assert data["age"] == 30
+    assert data["cultivation_level"] == 10
+    assert "injured" in data["tags"]
+    assert "battle" in data["tags"]
+
+    # 反序列化
+    restored = AvatarMetrics.from_save_dict(data)
+    assert restored.age == original.age
+    assert restored.cultivation_level == original.cultivation_level
+    assert restored.hp == original.hp
+    assert restored.tags == original.tags
+    assert restored.timestamp == original.timestamp
+
+
+def test_metric_tag_enum():
+    """测试 MetricTag 枚举"""
+    assert MetricTag.BREAKTHROUGH.value == "breakthrough"
+    assert MetricTag.INJURED.value == "injured"
+    assert MetricTag.RECOVERED.value == "recovered"
+    assert MetricTag.SECT_JOIN.value == "sect_join"
+    assert MetricTag.SECT_LEAVE.value == "sect_leave"
+    assert MetricTag.TECHNIQUE_LEARN.value == "technique_learn"
+    assert MetricTag.DEATH.value == "death"
+    assert MetricTag.BATTLE.value == "battle"
+    assert MetricTag.DUNGEON.value == "dungeon"
+
+
+def test_avatar_metrics_with_standard_tags():
+    """测试使用标准标签"""
+    metrics = AvatarMetrics(
+        timestamp=MonthStamp(50),
+        age=25,
+        cultivation_level=7,
+        cultivation_progress=300,
+        hp=80.0,
+        hp_max=100.0,
+        spirit_stones=200,
+        relations_count=4,
+        known_regions_count=5,
+        tags=[MetricTag.BREAKTHROUGH.value, MetricTag.BATTLE.value],
+    )
+
+    assert "breakthrough" in metrics.tags
+    assert "battle" in metrics.tags
+    assert len(metrics.tags) == 2
+
+
+def test_avatar_metrics_empty_tags():
+    """测试空标签列表"""
+    metrics = AvatarMetrics(
+        timestamp=MonthStamp(0),
+        age=0,
+        cultivation_level=0,
+        cultivation_progress=0,
+        hp=100.0,
+        hp_max=100.0,
+        spirit_stones=0,
+        relations_count=0,
+        known_regions_count=0,
+        tags=[],
+    )
+
+    assert metrics.tags == []
+    assert len(metrics.tags) == 0
+
+
+def test_avatar_metrics_multiple_tags():
+    """测试多个标签"""
+    tags = [
+        MetricTag.BREAKTHROUGH.value,
+        MetricTag.INJURED.value,
+        MetricTag.BATTLE.value,
+        "custom_event",  # 允许自定义标签
+    ]
+
+    metrics = AvatarMetrics(
+        timestamp=MonthStamp(1000),
+        age=100,
+        cultivation_level=15,
+        cultivation_progress=1000,
+        hp=50.0,
+        hp_max=500.0,
+        spirit_stones=10000,
+        relations_count=20,
+        known_regions_count=50,
+        tags=tags,
+    )
+
+    assert len(metrics.tags) == 4
+    assert "breakthrough" in metrics.tags
+    assert "injured" in metrics.tags
+    assert "battle" in metrics.tags
+    assert "custom_event" in metrics.tags