fix(health): floating window closes when opening TOC (gO)

fix(health): floating window closes when opening TOC (gO) #34794

Problem: Health check floating window gets closed when pressing 'gO' to show TOC because LSP floating preview system auto-closes on BufEnter events triggered by :lopen.

Solution: Temporarily disable BufEnter event for the current window during TOC operations and adjust window layout to prevent overlap.
(cherry picked from commit 28b7c2df52)

Co-authored-by: glepnir <glephunter@gmail.com>

runtime/lua/vim/treesitter/_headings.lua

@@ -83,8 +83,9 @@ local get_headings = function(bufnr)
   return headings
 end
 
+--- @param qf_height? integer height of loclist window
 --- Shows an Outline (table of contents) of the current buffer, in the loclist.
-function M.show_toc()
+function M.show_toc(qf_height)
   local bufnr = api.nvim_get_current_buf()
   local bufname = api.nvim_buf_get_name(bufnr)
   local headings = get_headings(bufnr)
@@ -102,7 +103,7 @@ function M.show_toc()
   end
   vim.fn.setloclist(0, headings, ' ')
   vim.fn.setloclist(0, {}, 'a', { title = 'Table of contents' })
-  vim.cmd.lopen()
+  vim.cmd.lopen({ count = qf_height })
   vim.w.qf_toc = bufname
   -- reload syntax file after setting qf_toc variable
   vim.bo.filetype = 'qf'