False-positive type error: `vim.cmd` callable table flagged as "table cannot match fun(...)"

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

### Which OS are you using?
Linux

### What is the issue affecting?
Diagnostics/Syntax Checking

### Expected Behaviour
lua-language-server should recognize callable tables (with a `__call` metamethod) as valid function values. Passing Neovim’s `vim.cmd` to `pcall` should not raise a type error.

### Actual Behaviour
lua-language-server reports a false-positive type error when `vim.cmd` (a callable table in Neovim) is passed to `pcall`:

Cannot assign `table` to parameter `fun(...):...unknown`
Type `table` cannot match `fun(...):...unknown`

### Reproduction steps
1. In Neovim, open a Lua buffer (e.g., `:new | set ft=lua`).
2. Insert the following code:

-- Works at runtime, but LuaLS flags the next line:
pcall(vim.cmd, "redrawtabline")
-- Diagnostic shown by LuaLS:
-- Cannot assign `table` to parameter `fun(...):...unknown`

3. Observe the diagnostic from lua-language-server.
4. Execute the code in Neovim (e.g., `:luafile %`) to confirm it runs without runtime errors.

### Additional Notes
- `vim.cmd` is a callable table provided by Neovim (implemented via `__call` metamethod). Direct calls like `vim.cmd("redrawtabline")` work at runtime. The false-positive only appears when passing `vim.cmd` as a function value (e.g., to `pcall`).
- Workarounds:

-- Wrap in a function
pcall(function() vim.cmd("redrawtabline") end)

-- or use the typed API
pcall(vim.api.nvim_cmd, { cmd = "redrawtabline" }, {})

- Please treat callable tables as functions for the purpose of type checking / inference.

Start by reproducing the diagnostic with pcall(vim.cmd, "redrawtabline") in a Neovim Lua buffer, then trace LuaLS diagnostics and type inference for callable tables with __call metamethods. Done means callable tables are accepted where function values are expected without hiding genuine type errors, and the reported reproduction no longer produces a diagnostic.

Written by the indexing model from the issue text.