chore: 工程化改造前的基线快照

在引入 uv 依赖管理、ruff 静态检查与格式化、pyright 类型检查之前，
先把当前可正常运行的状态固定下来，作为后续大规模自动改动的回滚点。

此时状态：97 项测试全绿，HTTP + WebSocket 多牧场服务器可用。

farm/storage.py

@@ -0,0 +1,129 @@
+"""存档读写。
+
+存档是纯 JSON，方便人工检查，也方便外部工具/AI 直接读取分析。
+写入采用"临时文件 + 原子替换"，避免中途崩溃导致存档损坏。
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import time
+from typing import Any, Dict, Optional, Tuple
+
+from .models import GameState
+
+SAVE_VERSION = 1
+
+
+def default_save_path() -> str:
+    """默认存档位置：项目根目录下的 saves/save.json。"""
+    root = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+    return os.path.join(root, "saves", "save.json")
+
+
+def save_state(state: GameState, path: Optional[str] = None) -> str:
+    """把状态写入磁盘，返回实际写入路径。"""
+    path = path or default_save_path()
+    directory = os.path.dirname(os.path.abspath(path))
+    os.makedirs(directory, exist_ok=True)
+
+    payload = {
+        "version": SAVE_VERSION,
+        "saved_at": time.strftime("%Y-%m-%d %H:%M:%S"),
+        "state": state.to_dict(),
+    }
+    # 注意：to_dict() 里的派生字段在读取时会被忽略，这里只取原始字段
+    payload["state"] = _raw_state(state)
+
+    tmp_path = path + ".tmp"
+    with open(tmp_path, "w", encoding="utf-8") as handle:
+        json.dump(payload, handle, ensure_ascii=False, indent=2)
+        handle.flush()
+        os.fsync(handle.fileno())
+    os.replace(tmp_path, path)
+    return path
+
+
+def _raw_state(state: GameState) -> Dict[str, Any]:
+    """导出可完整还原的原始字段（与 to_dict 的展示字段不同）。"""
+    return {
+        "day": state.day,
+        "gold": state.gold,
+        "level": state.level,
+        "exp": state.exp,
+        "ap": state.ap,
+        "feed": state.feed,
+        "plots": [
+            {
+                "index": p.index,
+                "crop": p.crop,
+                "growth": p.growth,
+                "moisture": p.moisture,
+                "planted_day": p.planted_day,
+            }
+            for p in state.plots
+        ],
+        "animals": [
+            {
+                "id": a.aid,
+                "kind": a.kind,
+                "fed": a.fed,
+                "progress": a.progress,
+                "starve": a.starve,
+                "pending": a.pending,
+            }
+            for a in state.animals
+        ],
+        "market": state.market,
+        "stats": {
+            "harvested": state.total_harvested,
+            "collected": state.total_collected,
+            "earned": state.total_earned,
+            "spent": state.total_spent,
+        },
+    }
+
+
+def load_state(path: Optional[str] = None) -> Tuple[Optional[GameState], str]:
+    """读取存档。
+
+    返回 ``(state, message)``；失败时 ``state`` 为 None 并给出原因，
+    调用方应当降级为"开新档"而不是崩溃。
+    """
+    path = path or default_save_path()
+    if not os.path.exists(path):
+        return None, f"未找到存档 {path}"
+
+    try:
+        with open(path, "r", encoding="utf-8") as handle:
+            payload = json.load(handle)
+    except (OSError, json.JSONDecodeError) as exc:
+        return None, f"存档无法解析：{exc}"
+
+    if not isinstance(payload, dict):
+        return None, "存档格式错误：根节点不是对象"
+
+    version = payload.get("version", 0)
+    if version != SAVE_VERSION:
+        return None, f"存档版本不兼容（文件 v{version}，当前 v{SAVE_VERSION}）"
+
+    raw = payload.get("state")
+    if not isinstance(raw, dict):
+        return None, "存档缺少 state 字段"
+
+    try:
+        state = GameState.from_dict(raw)
+    except (TypeError, ValueError, KeyError) as exc:
+        return None, f"存档内容异常：{exc}"
+
+    return state, f"已载入存档（第 {state.day} 天）"
+
+
+def delete_save(path: Optional[str] = None) -> bool:
+    path = path or default_save_path()
+    try:
+        os.remove(path)
+        return True
+    except OSError:
+        return False