fix(client): honor count on Neovim Index; log third re-audit findings

Third audit pass (config/mappings/commands vs vimwiki master) confirmed all
recent range/bang/visual and diary-week work is present and correct in both
clients, with no regressions, and that Neovim does bind the text objects.

It surfaced one real oversight: the Neovim Vimwiki/NuwikiIndex commands still
read vim.v.count (always 0 in command context) instead of <count> — the same
bug the TabIndex fix addressed, but Index was missed. Fixed both to <count>,
so :2NuwikiIndex now opens wiki 2.

Gap doc updated: new open item (VimwikiSplitLink/VSplitLink missing upstream
-nargs=*), mouse-maps-opt-in recorded as an intentional divergence, and the
third-pass summary. Suites green — nvim 274, vim 266+18.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ftplugin/vimwiki.vim

@@ -384,7 +384,7 @@ endif
 " `nuwiki.commands` that either issues a `workspace/executeCommand`
 " or, for client-side operations, calls `vim.lsp.buf.*` directly.
 
-command! -buffer -count VimwikiIndex      lua require('nuwiki.commands').wiki_index(vim.v.count)
+command! -buffer -count VimwikiIndex      lua require('nuwiki.commands').wiki_index(<count>)
 command! -buffer -count VimwikiTabIndex   lua require('nuwiki.commands').wiki_tab_index(<count>)
 command! -buffer        VimwikiUISelect   lua require('nuwiki.commands').wiki_ui_select()
 command! -buffer        VimwikiDiaryIndex lua require('nuwiki.commands').diary_index()
@@ -460,7 +460,7 @@ command! -buffer        VimwikiPasteUrl            lua require('nuwiki.commands'
 command! -buffer        VimwikiCatUrl              lua require('nuwiki.commands').cat_url()
 
 " Canonical :Nuwiki* aliases — P10.
-command! -buffer -count NuwikiIndex      lua require('nuwiki.commands').wiki_index(vim.v.count)
+command! -buffer -count NuwikiIndex      lua require('nuwiki.commands').wiki_index(<count>)
 command! -buffer -count NuwikiTabIndex   lua require('nuwiki.commands').wiki_tab_index(<count>)
 command! -buffer        NuwikiUISelect   lua require('nuwiki.commands').wiki_ui_select()
 command! -buffer        NuwikiDiaryIndex lua require('nuwiki.commands').diary_index()