[Bug] Union when combine table with classified type. Attributes of table are hidden.

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### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Windows

### What is the issue affecting?

Type Checking

### Expected Behaviour

```lua
local data = {}
function data:set(k, v)
rawset(self, k, v)
end

--- @class Person
local Person = {}
function Person:speak() end

--- @generic T
--- @param t T
--- @return T|Person
function merge(t, p)
-- ...
end

local m = merge(data, Person)
m:set -- Completion should show [set(k, v)] 应该提示 set(k,v)，对应 data:set(k,v)
```

### Actual Behaviour

```lua
local data = {}
function data:set()
end

--- @class Person
local Person = {}
function Person:speak() end

--- @generic T
--- @param t T
--- @return T|Person
function merge(t, p)
-- ...
end

local m = merge(data, Person)
m:set -- doesn't complete this method, 没显示，只有一个单纯的文本补全
```

But .... 但是... 你换成 {} 而不去声明 `@class Person` 倒是会有的

```lua
local data = {}
function data:set()
end

local Person = {}
function Person:speak() end

--- @generic T
--- @param t T
--- @return T|{speak: function} !!!!! See here !!! 看这里，换成纯粹的 table 到会有
function merge(t, p)
-- ...
end

local m = merge(data, Person)
m:set -- Completion is right and show [set(k,v)]，补全正常显示
```

I guess the `@class Person` hides the origin type.

我认为 `@class Person` 把原本的 data 表 属性都给给覆盖掉了。

而且还有个诡异现象，如果 data 给一些 默认值：

`local data = {value = 123}`

不管哪种方式 都能把 默认属性 给补出来。

这很明显这个 luals 的 union 组合有 bug！

### Reproduction steps

See obove

### Additional Notes

_No response_

### Log File

_No response_

Reproduce the issue in the Visual Studio Code extension using the provided Lua examples, comparing the union with @class Person against the inline table type. Trace type checking and completion handling for the result of merge when m:set is queried. Done means completion includes data:set while retaining Person members such as speak.

Written by the indexing model from the issue text.