Hover preview incorrectly narrows union of literal and type

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### 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_

Reproduce the issue in a Lua file opened in the Visual Studio Code extension by hovering over the aliases and variables shown in the report. Trace the hover type-rendering path for unions combining literal values with integer or string, and verify that the previews retain the overall type alongside the literal members.

Written by the indexing model from the issue text.