bug: clarify docs that copilot LSP is only a requirement if NES is enabled

[dwf]

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Neovim version (nvim -v)

0.12.3

Operating system/version

Linux

Describe the bug

This is deducible from the docs but not stated explicitly under "Requirements": Copilot LSP installation is not required with NES disabled, i.e. to only use the CLI tool functionality. The docs do state that the CLI functionality does not depend on Copilot at all, and is usable with NES disabled, but this is inconsistent with "Requirements".

As it stands, this is causing nixpkgs to list copilot-language-server as a hard dependency, which requires one to then globally allow unfree packages or allowlist copilot-language-server.

Steps To Reproduce

N/A, it's a documentation issue

Expected Behavior

The documentation should clearly state under what circumstances/usages the Copilot LSP is required.

Repro

vim.env.LAZY_STDPATH = ".repro"
load(vim.fn.system("curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua"))()

require("lazy.minit").repro({
  spec = {
    { "folke/sidekick.nvim", opts = {} },
    -- add any other plugins here
  },
})