Properties (getter/setter) support

还没有人认领这个 Issue。

Lua's variables can act as C#-like properties by setting `__newindex` appropriately.

Getters and setters occasionally have different type signatures. However, the `@field` annotation can only represent one type.

```lua
-- hoge.meta.lua

---@meta

---@class Point
---@field x number
---@field y number
Point = {}

---@class Hoge
---@field position Point ⚠️ actually a property
Hoge = {}

---@return Hoge
function new_hoge() end
```

```lua
-- main.lua

local hoge = new_hoge()
hoge.position = { 3, 7 } -- emits "Missing required fields in type `Point`: `x`, `y`"
print(hoge.position.x) -- 3.0
print(hoge.position.y) -- 7.0
```

(Full sample program is [here](https://codeberg.org/haruomaki/luaproperty))

It should be annotated as "`position`'s setter receives a `table`, and its getter returns a `Point`."

How about adding a new syntax to describe this?

先从 hoge.meta.lua 和 main.lua 中的注解示例开始，然后重现将一个表赋值给 hoge.position 时的诊断。该 issue 未指明任何仓库文件或测试，因此必须找到相关的注解和类型检查入口。完成的标准是：注解语法可以表达不同的 setter 和 getter 类型，并且示例赋值不再报告缺少 Point 字段。

由索引模型根据 Issue 内容生成。