feat: add Elixir comment and doc-attribute extraction

[C-Sinclair]

Adds Elixir (.ex, .exs) to the tree-sitter comment extractors.

Why the doc attributes, not just the comments

Elixir has no documentation comment syntax. Its published API documentation lives in module attributes holding a string or a heredoc:

defmodule Session do
  @moduledoc """
  A scheduled period of care delivery.
  """

  @doc "Books a session for a client."
  def book(client), do: ...
end

That is what mix docs renders and what a reader of a module reads first, so extracting only # comments would see the asides and none of the documentation.

Both are extracted. Comments keep the usual scopes; the attributes get a doc meta scope, so text.comment.doc.block can be held to a different standard than an implementation note, or excluded on its own via IgnoredScopes. @moduledoc, @doc, @typedoc and @shortdoc are covered; @doc false and @doc since: "1.0.0" carry no prose and the queries require a string or sigil argument, so neither matches.

Predicate-only captures

The attribute name is what decides whether a node is documentation, and the prose is a different node — so the query has to test one node and capture another. #match? can only test a captured node, so this needs a capture that is tested but not linted.

query.go now skips captures whose name begins with _, which is the convention tree-sitter itself uses for internal captures. Without it, the query has to capture the whole @moduledoc """...""" and take the delimiters off with Delims — which for the single-quoted @doc "..." form would also strip any quote written inside the prose.

With it, the queries capture quoted_content (the body of the string) and the extracted text needs no delimiter stripping at all. Delims is just #.

This is a small behaviour change to shared code: any existing query using an _-prefixed capture name would stop having that capture linted. I could find none in-tree, and linting a capture that exists for a predicate looks like the unintended reading, but flag it in case you'd rather have it behind a language flag.

Notes

• github.com/smacker/go-tree-sitter/elixir is already vendored, so this adds no dependency.
• .heex (Phoenix HTML templates) is deliberately left alone — no grammar for it in the set, and mapping it onto HTML would reduce it to <!-- --> comments.

Tests

• testdata/comments/{in,out}/8.ex, 9.exs — extraction fixtures covering heredoc docs, the single-quoted form, sigil docs (~S"""), a line-comment run, a trailing comment, and the prose-free attributes.
• testdata/e2e/lint.yaml — an elixir case against testdata/fixtures/formats/test.ex; all seven reported columns are exact.
• TestPredicateOnlyCapture and TestDocAttributesWithoutProse in comments_test.go.

go test ./internal/... is green.

Happy to split the query.go change into its own commit or PR if you'd prefer to take them separately.