Root .formatter.exs support for umbrella projects

[superhawk610]

Describe the bug

I have an umbrella project with a single .formatter.exs at the root. When Dexter formats-on-save a file with Phoenix LiveView's attr macro, it changes this:

attr :name, :string

to this

attr(:name, :string)

To reproduce

Here's my file tree:

| mix.exs
| .formatter.exs
/ apps
  / app_web
    | mix.exs
    / lib
      | component.ex

Expected behavior

I'd expect the locals_without_parens (from import_deps) present in the root-level .formatter.exs to prevent that.

Debug logs

2026/04/15 11:21:48 Formatter: started persistent process for /apps/app_web/.formatter.exs (pid 29467)

Environment

• Dexter version (dexter --version): 0.5.3
• Elixir version (elixir --version): 1.19.5
• Editor and version: Windsurf 1.110.1
• OS: macOS Tahoe 26.4

It appears that when attempting to resolve the nearest .formatter.exs, traversal stops when a directory containing a mix.exs is reached. The expected file layout for running mix format for umbrella apps isn't super well-documented, but this setup (a single .formatter.exs at the umbrella root) seems at least somewhat common. When no nested config file exists under apps/{app}/.formatter.exs, I'd expect the LSP to fallback to the umbrella root's file instead.

[JesseHerrick]

Code to fix this was added in #50 as part of the Erlang docs feature. Thanks again for the bug report and fix! Let me know if you have any more issues with this.