fix(rust): drop incompatible root_dir under native_lsp_config

[Mic92]

📑 Description

With astrolsp native_lsp_config enabled, lsp_opts("rust_analyzer") returns the full vim.lsp.config table including nvim-lspconfig's root_dir(bufnr, on_dir) function. rustaceanvim calls its root_dir with (file_name, default_fn) instead, causing on every rust file open:

Error executing lua callback: .../lsp/rust_analyzer.lua:89: Invalid 'buffer': Expected Lua number
stack traceback:
        [C]: in function 'nvim_buf_get_name'
        .../nvim-lspconfig/lsp/rust_analyzer.lua:89: in function 'root_dir'
        .../rustaceanvim/lua/rustaceanvim/cargo.lua:127: in function 'get_config_root_dir'
        .../rustaceanvim/lua/rustaceanvim/lsp/init.lua:171: in function 'start'

This drops root_dir from the forwarded opts so rustaceanvim falls back to its own cargo-aware root detection. Guarded on native_lsp_config so legacy-path users who set a custom root_dir via opts.config.rust_analyzer are unaffected.

• Tested with native_lsp_config = true — rust-analyzer attaches, no errors
• Tested with native_lsp_config = false (default) — rust-analyzer attaches, root_dir untouched, no behavior change

📖 Additional Information

This becomes relevant for all users once native_lsp_config is the default (astrolsp v4, see AstroNvim/astrolsp#35).

The dart, scala, typescript-deno and moonbit packs also call astrolsp.lsp_opts and may have similar issues, but I have not tested those.

[github-actions]

Review Checklist

Does this PR follow the [Contribution Guidelines](development guidelines)? Following is a partial checklist:

Proper conventional commit scoping:

• If you are adding a new plugin, the scope would be the name of the category it is being added into. ex. feat(utility): added noice.nvim plugin

• If you are modifying a pre-existing plugin or pack, the scope would be the name of the plugin folder. ex. fix(noice-nvim): fix LSP handler error

• Pull request title has the appropriate conventional commit type and scope where the scope is the name of the pre-existing directory in the project as described above

• README is properly formatted and uses fenced in links with <url> unless they are inside a [title](url)

• Entry returns a single plugin spec with the new plugin as the only top level spec (not applicable for recipes or packs).

• Proper usage of opts table rather than setting things up with the config function.

• Proper usage of specs table for all specs that are not dependencies of a given plugin (not applicable for recipes or packs).

[rami3l]

I second this; this fix is also a necessary step to bump rustaceanvim to v7 and higher.

FTR I've already got rustaceanvim v9 running with some tiny modifications to the current pack, and I'd love to upstream the rest when this fix lands.

[Uzaaft]

@Mic92 Fix the conflicts and I'll merge this.

[rami3l]

Since AstroNvim/astrolsp#35 has been merged, astrolsp.config.native_lsp_config no longer exists, so this line should simply be:

Suggested change

	if astrolsp_avail and astrolsp.config.native_lsp_config then astrolsp_opts.root_dir = nil end
	astrolsp_opts.root_dir = nil