feat: 完善扫描器、exec 及 schema 相关功能

- exec/scanner: 用 *interface{} 替换 **json.RawMessage 扫描目标，兼容 DuckDB 返回 map[string]interface{} 的场景；新增 toJSONRawMessage 转换函数
- exec/scanner: ScanVal 支持结构体指针，通过 JSON 中间层转换（DuckDB STRUCT 列）
- exec/scanner: 将 *sql.RawBytes 和 *[]byte 的处理从 ScanValContext 移入 scanner.ScanVal
- exec/query_executor: 简化 ScanValContext，移除私有 scan 方法
- exec: 补充 scanner 级别 ScanVal 测试用例
- internal/util/reflect: 重写 SafeSetVarValue，修复非指针 src 及 nil 指针字段的 panic
- internal/util/column_map: 恢复非匿名带标签结构体字段的展开逻辑
- schema: 新增 vector 列类型支持
- engine: 补充 DuckDB 相关配置
- dialect/sqlite3/vtab: 完善虚拟表适配器
- 各方言测试改用 sqlmock 虚拟连接

schema/dialect/duckdb/duckdb_test.go

@@ -81,8 +81,9 @@ func (t *duckDBTest) TestCompileCreate() {
 	sql := t.schema.CompileCreate(bp)
 
 	t.Equal([]string{
-		"CREATE TABLE \"users\" (\n" +
-			"\"id\" BIGSERIAL NOT NULL PRIMARY KEY,\n" +
+		"CREATE SEQUENCE IF NOT EXISTS \"users_id_seq\"",
+		"CREATE TABLE IF NOT EXISTS \"users\" (\n" +
+			"\"id\" BIGINT DEFAULT nextval('users_id_seq') PRIMARY KEY,\n" +
 			"\"enabled\" BOOLEAN NOT NULL DEFAULT '1',\n" +
 			"\"created_user\" CHAR(36) NOT NULL DEFAULT '00000000-0000-0000-0000-000000000000',\n" +
 			"\"owned_user\" CHAR(36) NOT NULL DEFAULT '00000000-0000-0000-0000-000000000000',\n" +
@@ -90,6 +91,13 @@ func (t *duckDBTest) TestCompileCreate() {
 			"\"updated_at\" TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,\n" +
 			"\"deleted_at\" TIMESTAMP NULL\n" +
 			")",
+		"COMMENT ON COLUMN \"users\".\"id\" IS 'ID'",
+		"COMMENT ON COLUMN \"users\".\"enabled\" IS '是否有效'",
+		"COMMENT ON COLUMN \"users\".\"created_user\" IS '创建者'",
+		"COMMENT ON COLUMN \"users\".\"owned_user\" IS '拥有者'",
+		"COMMENT ON COLUMN \"users\".\"created_at\" IS '创建时间'",
+		"COMMENT ON COLUMN \"users\".\"updated_at\" IS '更新时间'",
+		"COMMENT ON COLUMN \"users\".\"deleted_at\" IS '删除时间'",
 	}, sql)
 
 	t.T().Log(sql)
@@ -109,6 +117,9 @@ func (t *duckDBTest) TestCompileAdd() {
 			"ADD COLUMN \"name\" VARCHAR(50) NOT NULL,\n" +
 			"ADD COLUMN \"age\" SMALLINT NOT NULL DEFAULT '18',\n" +
 			"ADD COLUMN \"sex\" VARCHAR(1) NOT NULL DEFAULT '0'",
+		"COMMENT ON COLUMN \"users\".\"name\" IS '用户名'",
+		"COMMENT ON COLUMN \"users\".\"age\" IS '年龄'",
+		"COMMENT ON COLUMN \"users\".\"sex\" IS '性别'",
 	}, sql)
 
 	t.T().Log(sql)