refactor: 删除 config.json + 内置工具抽离 + 统一接口

删除:
  - config.rs / config.json（AppConfig/LmStudioConfig）
  - LM Studio 残留（lmstudio.rs 已在之前删除）
  - main.rs 中散落的内置工具 match arms

新增:
  - src/tools/builtin.rs — BuiltinRegistry 统一切入
    get_current_datetime、manage_memos 为核心内置工具
    统一参数校验、风险等级、错误返回

改动:
  - 模型名直接从 DEEPSEEK_MODEL 环境变量读取
  - builtin 工具与 skills 工具统一经过 SkillRegistry 审批
  - query_capabilities 合并内置 + 外部技能列表

resources/skills/get_current_datetime/SKILL.md

@@ -1,26 +1,8 @@
 # get_current_datetime
-
-获取当前日期时间（北京时间 UTC+8）。
-
+获取当前日期时间（UTC+8）。内置 Rust 实现，无脚本依赖。
 ## Risk Level
 Low
-
-## Parameters
-```json
-{
-  "type": "object",
-  "properties": {
-    "format": {
-      "type": "string",
-      "description": "时间格式: full | date | time",
-      "enum": ["full", "date", "time"],
-      "default": "full"
-    }
-  }
-}
-```
-
 ## Execute
 ```bash
-scripts/datetime.sh
+# Builtin: Rust
 ```

resources/skills/get_current_datetime/scripts/datetime.sh

@@ -1,16 +0,0 @@
-#!/bin/bash
-# 读取 stdin JSON 参数
-read -r input
-format=$(echo "$input" | python3 -c "
-import sys, json
-try:
-    d = json.load(sys.stdin)
-    print(d.get('format', 'full'))
-except: print('full')
-" 2>/dev/null || echo "full")
-
-case "$format" in
-  date)    TZ='Asia/Shanghai' date '+{"datetime": "%Y-%m-%d"}' ;;
-  time)    TZ='Asia/Shanghai' date '+{"datetime": "%H:%M:%S"}' ;;
-  *)       TZ='Asia/Shanghai' date '+{"datetime": "%Y-%m-%d %H:%M:%S"}' ;;
-esac

resources/skills/manage_memos/SKILL.md

@@ -1,36 +1,8 @@
 # manage_memos
-
-管理备忘录：添加、列出、删除。
-
-备忘录存储在 `.data/memos.json` 文件中。
-
+管理备忘录（添加/列出/删除）。内置 Rust 实现，无脚本依赖。
 ## Risk Level
 High
-
-## Parameters
-```json
-{
-  "type": "object",
-  "properties": {
-    "action": {
-      "type": "string",
-      "description": "操作类型",
-      "enum": ["add", "list", "delete"]
-    },
-    "content": {
-      "type": "string",
-      "description": "备忘内容（add 时需要）"
-    },
-    "id": {
-      "type": "integer",
-      "description": "备忘编号（delete 时需要）"
-    }
-  },
-  "required": ["action"]
-}
-```
-
 ## Execute
 ```bash
-scripts/memo.sh
+# Builtin: Rust
 ```

resources/skills/manage_memos/scripts/memo.sh

@@ -1,58 +0,0 @@
-#!/bin/bash
-# 备忘录管理 — 存储 .data/memos.json
-MEMO_FILE=".data/memos.json"
-mkdir -p "$(dirname "$MEMO_FILE")"
-[ ! -f "$MEMO_FILE" ] && echo '[]' > "$MEMO_FILE"
-
-read -r INPUT
-export MEMO_INPUT="$INPUT"
-
-python3 - "$MEMO_FILE" << 'PYEOF'
-import sys, json, os, datetime
-
-path = sys.argv[1]
-input_raw = os.environ.get('MEMO_INPUT', '{}')
-
-try: req = json.loads(input_raw)
-except:
-    print('无效的 JSON 输入')
-    sys.exit(1)
-
-action = req.get('action', 'list')
-content = req.get('content', '')
-memo_id = req.get('id', '')
-
-data = json.load(open(path)) if os.path.exists(path) and os.path.getsize(path) > 0 else []
-
-if action == 'add':
-    if not content:
-        print('请提供 content 参数')
-        sys.exit(1)
-    next_id = max([m.get('id', 0) for m in data], default=0) + 1
-    data.append({'id': next_id, 'content': content, 'created_at': datetime.datetime.now().isoformat()})
-    json.dump(data, open(path, 'w'), ensure_ascii=False, indent=2)
-    print(f'已添加备忘录 #{next_id}')
-
-elif action == 'list':
-    if not data:
-        print('暂无备忘录')
-    else:
-        for m in data:
-            ts = m.get('created_at', '?')[:16]
-            print(f"#{m['id']} [{ts}] {m['content']}")
-
-elif action == 'delete':
-    if not memo_id:
-        print('请提供 id 参数')
-        sys.exit(1)
-    new = [m for m in data if str(m.get('id', '')) != str(memo_id)]
-    if len(new) == len(data):
-        print(f'未找到备忘 #{memo_id}')
-    else:
-        json.dump(new, open(path, 'w'), ensure_ascii=False, indent=2)
-        print(f'已删除备忘 #{memo_id}')
-
-else:
-    print(f'未知操作: {action}（支持: add, list, delete）')
-    sys.exit(1)
-PYEOF