Problem:
The check for concealing paths in TOCs in the qf syntax file fails
because the TOC tile has changed.
Solution:
Force the qf syntax file to be reloaded after the qf_toc variable
has been set, so that the it can apply the correct settings.
Using the explicit qf_toc key, already used in the syntax file, instead
of the title is less prone to breaking.
It was also already being set for man pages but it had no effect because
the syntax file had already been loaded when the variable was set.
Fixes#33733
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.
