fix(treesitter): highlight group for EditQuery captures #36265

fix(treesitter): more distinctive highlight for EditQuery captures

Problem: EditQuery shows captures in the source buffer using the Title
highlight group, which could be too similar to Normal.

Solution: Use a virtual text diagnostic highlight group: they are
displayed in a similar manner to the query captures so we can assume
that the color scheme should have appropriate styling applied to make
them visible.

runtime/lua/vim/treesitter/dev.lua

@@ -608,7 +608,7 @@ local function update_editor_highlights(query_win, base_win, lang)
           end_col = end_col,
           hl_group = 'Visual',
           virt_text = {
-            { capture_name, 'Title' },
+            { capture_name, 'DiagnosticVirtualTextHint' },
           },
         })
       end

runtime/lua/vim/treesitter/query.lua

@@ -1196,9 +1196,11 @@ end
 --- Can also be shown with the [:EditQuery]() command. `:EditQuery <tab>` completes available
 --- parsers.
 ---
---- If you move the cursor to a capture name ("@foo"), text matching the capture is highlighted in
---- the source buffer. The query editor is a scratch buffer, use `:write` to save it. You can find
---- example queries at `$VIMRUNTIME/queries/`.
+--- If you move the cursor to a capture name ("@foo"), text matching the capture is highlighted
+--- with |hl-DiagnosticVirtualTextHint| in the source buffer.
+---
+--- The query editor is a scratch buffer, use `:write` to save it. You can find example queries
+--- at `$VIMRUNTIME/queries/`.
 ---
 --- @param lang? string language to open the query editor for. If omitted, inferred from the current buffer's filetype.
 function M.edit(lang)