refactor(todo): 去除 MySQL 依赖，改为 JSON 本地存储

- 数据存储: ~/.local/share/todo/tasks.json 纯字符串数组
- 操作简化: 仅保留 add/list/done，无状态/优先级/归档
- 新增 scripts/validate.py 校验脚本 (格式/结构/去重)
- 新增 schema/tasks.schema.json
- 删除 references/setup.md (MySQL 配置指南)

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

todo/scripts/validate.py

@@ -0,0 +1,142 @@
+#!/usr/bin/env python3
+"""校验 ~/.local/share/todo/tasks.json 的格式、结构和完整性。
+
+退出码:
+  0 - 校验通过
+  1 - 校验失败（错误信息输出到 stderr）
+
+用法:
+  python3 validate.py [文件路径]
+  默认路径: ~/.local/share/todo/tasks.json
+"""
+
+import json
+import os
+import sys
+from pathlib import Path
+
+DEFAULT_PATH = Path.home() / ".local" / "share" / "todo" / "tasks.json"
+SCHEMA_PATH = Path(__file__).parent.parent / "schema" / "tasks.schema.json"
+
+
+def load_json(path: Path) -> tuple[dict | None, str | None]:
+    """加载并解析 JSON 文件。"""
+    if not path.exists():
+        return None, f"文件不存在: {path}"
+    try:
+        with open(path, "r", encoding="utf-8") as f:
+            data = json.load(f)
+        return data, None
+    except json.JSONDecodeError as e:
+        return None, f"JSON 格式错误: {e}"
+
+
+def load_schema() -> tuple[dict | None, str | None]:
+    """加载 JSON Schema。"""
+    if not SCHEMA_PATH.exists():
+        return None, f"Schema 文件不存在: {SCHEMA_PATH}"
+    try:
+        with open(SCHEMA_PATH, "r", encoding="utf-8") as f:
+            return json.load(f), None
+    except json.JSONDecodeError as e:
+        return None, f"Schema 格式错误: {e}"
+
+
+def validate_structure(data: dict) -> list[str]:
+    """校验数据结构。"""
+    errors = []
+
+    if not isinstance(data, dict):
+        errors.append("顶层必须是对象")
+        return errors
+
+    if "tasks" not in data:
+        errors.append("缺少必需字段 'tasks'")
+        return errors
+
+    tasks = data["tasks"]
+    if not isinstance(tasks, list):
+        errors.append("'tasks' 必须是数组")
+        return errors
+
+    for i, item in enumerate(tasks):
+        if not isinstance(item, str):
+            errors.append(f"tasks[{i}] 必须是字符串，实际类型: {type(item).__name__}")
+        elif len(item.strip()) == 0:
+            errors.append(f"tasks[{i}] 不能为空字符串")
+
+    return errors
+
+
+def validate_duplicates(tasks: list[str]) -> list[str]:
+    """校验任务是否有重复（大小写不敏感）。"""
+    errors = []
+    seen = {}
+    for i, task in enumerate(tasks):
+        key = task.strip().lower()
+        if key in seen:
+            errors.append(f"tasks[{i}] '{task}' 与 tasks[{seen[key]}] 重复")
+        else:
+            seen[key] = i
+    return errors
+
+
+def validate_schema(data: dict) -> list[str]:
+    """使用 JSON Schema 校验（如果 jsonschema 可用）。"""
+    try:
+        import jsonschema
+    except ImportError:
+        # jsonschema 未安装，跳过 schema 校验
+        return []
+
+    schema, err = load_schema()
+    if err:
+        return [f"Schema 校验跳过: {err}"]
+
+    errors = []
+    try:
+        jsonschema.validate(instance=data, schema=schema)
+    except jsonschema.ValidationError as e:
+        errors.append(f"Schema 校验失败: {e.message}")
+    except jsonschema.SchemaError as e:
+        errors.append(f"Schema 定义错误: {e.message}")
+
+    return errors
+
+
+def main() -> int:
+    path = Path(sys.argv[1]) if len(sys.argv) > 1 else DEFAULT_PATH
+
+    # 1. JSON 格式校验
+    data, err = load_json(path)
+    if err:
+        print(err, file=sys.stderr)
+        return 1
+
+    # 2. 结构校验
+    errors = validate_structure(data)
+    if errors:
+        for e in errors:
+            print(f"结构错误: {e}", file=sys.stderr)
+        return 1
+
+    # 3. JSON Schema 校验
+    schema_errors = validate_schema(data)
+    if schema_errors:
+        for e in schema_errors:
+            print(f"Schema 错误: {e}", file=sys.stderr)
+        return 1
+
+    # 4. 去重校验
+    dup_errors = validate_duplicates(data["tasks"])
+    if dup_errors:
+        for e in dup_errors:
+            print(f"重复错误: {e}", file=sys.stderr)
+        return 1
+
+    print(f"校验通过: {path} ({len(data['tasks'])} 个任务)")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())