Hover preview incorrectly narrows union of literal and type

まだ誰も着手していません。

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

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Linux

### What is the issue affecting?

Hover

### Expected Behaviour

```lua
---@alias inttype -1 | 0 | integer
---@type inttype
local intvar = 1
---@alias stringtype "a" | "b" | string
---@type stringtype
local stringvar = "x"
```

I expect the hover previews for `inttype`, `intvar`, `stringtype`, and `stringvar` to show the full expansion of the `intttype` and `stringtype` aliases, something like

```
inttype:
| -1
| 0
| integer
```
and
```
stringtype:
| "a"
| "b"
| string
```

### Actual Behaviour

The rendered preview of the type aliases omits the overall type:
```
inttype:
| -1
| 0
```
and
```
stringtype:
| "a"
| "b"
```

This is especially weird because if those were the actual type definitions then the two assignments in the example would be type errors, which they are not.

### Reproduction steps

Put the code above into a Lua file in vscode with the language server extension running. Hover over the type aliases and the variables. The problem happens with just one literal in each union, two aren't required but I thought they illustrated the preview problem better.

### Additional Notes

The reason I want to make "useless" union types like this is for hinting to humans that those specific values are special in some way.

### Log File

_No response_

Visual Studio Code拡張機能で開いたLuaファイル内で、報告に示されているエイリアスと変数にカーソルを合わせて問題を再現します。リテラル値とintegerまたはstringを組み合わせるunionのホバー時の型レンダリング経路を追跡し、プレビューにリテラルメンバーとともに全体の型も保持されることを確認します。

索引モデルが issue の本文から書いたものです。