Exact Classes Do Not Autocomplete Methods

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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?

Completion

### Expected Behaviour

Autocomplete should complete methods on instances of (exact) classes.

Expected completion for a normal class:

### Actual Behaviour

Methods are not completed.


### Reproduction steps

VSCode project with v3.11.0 plugin.

All defaults, no `.luarc.json`.

Ctrl-space at last line.

```lua
---@class (exact) Point
--@class Point
---@field x number
---@field y number
local Point = {}

function Point:new(o)
o = o or {}

setmetatable(o, self)
self.__index = self ---@diagnostic disable-line: inject-field

return o
end

---@param i integer
function Point:add(i)
self.x = self.x + i
end

---@type Point
local point = Point:new({ x = 1, y = 2 })

point:
```

### Additional Notes

Many thanks for all the fantastic work - luals makes me so much more productive!

### Log File

[log.tar.gz](https://github.com/user-attachments/files/17549561/log.tar.gz)

Reproduce the issue in a Visual Studio Code project with the v3.11.0 plugin using the provided Point class and Ctrl-space at the final line. Compare completion for the exact class with the normal class example. Done means the add method is offered for completion on the Point instance.

Written by the indexing model from the issue text.