Problem: Argument type mismatches are excluded from EmmyLua checks.

Solution: Correct runtime annotations and calls, document local checker
workarounds, and enable the diagnostic.

AI-assisted

Enable checks for unused code, deprecated calls, return types, and
annotations.

Fix the warnings and replace the deprecated highlight function. Keep
exceptions where old APIs are still needed or the checker gets it wrong.

AI-assisted

Problem:
`:EditQuery` command accepts a language argument, but it doesn't
highlight properly for injected languages.

Solution:
- Fully parse with the root language and then filter the query on the
  child trees that are of the language requested.
- Also support completion (`EditQuery <tab>`).

Type fixes caught by emmylua

Problem: No way to check the version of a treesitter parser.

Solution: Add version metadata (ABI 15 parsers only) as well as parser state count and supertype information (ABI 15) in `vim.treesitter.language.inspect()`. Also graduate the `abi_version` field, as this is now the official upstream name.

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Co-authored-by: Christian Clason <c.clason@uni-graz.at>

Problem: It's difficult to navigate large structured text files (vim
help, checkhealth, Markdown).

Solution: Support `gO` for table of contents and `]]`/`[[` for moving
between headings for all these filetypes using treesitter queries.

Refactor: colorization of highlight groups is moved to the `help` ftplugin
while headings-related functionality is implemented in a private
`vim.treesitter` module for possible future use for other filetypes.

Problem:
The `vim.treesitter.language.add` function returns
a error message even when it succeeds.

Solution:
Don't return error message on success.