fix(parity): fifth-pass re-audit — VimwikiGoto nargs, autowriteall, table_auto_fmt

Closes the actionable fifth-pass findings (gap doc updated):

- VimwikiGoto / NuwikiGoto: -nargs=1 -> -nargs=* in all four defs. Was a
  real bug — `:VimwikiGoto` raised E471, `:VimwikiGoto My Page` raised E488,
  and the handler's empty-arg prompt fallback was unreachable. Both clients
  already prompt on empty, so -nargs=* (keeping -complete=pages) restores
  upstream behavior.

- autowriteall (upstream default ON): while a wiki buffer is current, mirror
  Vim's global 'autowriteall' (auto-save on page switch / :make), restoring
  the prior value on leave. Neovim via ftplugin.lua setup_autowriteall
  (BufEnter/BufLeave) gated by the `autowriteall` setup option; Vim via the
  NuwikiAutoWriteAll augroup gated by g:nuwiki_autowriteall.

- table_auto_fmt (upstream default ON): re-align the table under the cursor
  on InsertLeave. Both clients, gated by `table_auto_fmt` / g:nuwiki_table_auto_fmt,
  guarded on the cursor line containing `|` before the async table_align.

Also logged (no code): VimwikiRenameFile missing -nargs=? (subsumed by the
LSP-rename divergence), table_reduce_last_col, user_htmls, hl_headers/
hl_cb_checked, and a commentstring value-mismatch note. Mappings audit clean.

The Neovim harness disables table_auto_fmt in setup (its async re-align would
perturb the deterministic table-nav keystroke cases); its wiring is verified
on a throwaway scratch buffer instead. Docs (README + doc/nuwiki.txt) updated.
Tests: cmd.VimwikiGoto_accepts_multiword, config.autowriteall_applied,
config.table_auto_fmt_autocmd. Neovim 293, Vim 285/18/21 pass.

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

development/tests/test-keymaps.sh

@@ -39,8 +39,14 @@ cat > "$INIT" <<EOF
 vim.opt.runtimepath:prepend('$REPO_ROOT')
 vim.g.nuwiki_binary_path = '$BIN'
 -- Enable the opt-in mouse mappings so the harness can assert the full
--- documented mapping surface (doc §6 mouse group).
-require('nuwiki').setup({ wiki_root = '$TMP/wiki', mappings = { mouse = true } })
+-- documented mapping surface (doc §6 mouse group). table_auto_fmt is off here
+-- so its async on-InsertLeave re-align doesn't perturb the deterministic
+-- table-nav keystroke cases (its wiring is verified on a scratch buffer).
+require('nuwiki').setup({
+  wiki_root = '$TMP/wiki',
+  mappings = { mouse = true },
+  table_auto_fmt = false,
+})
 EOF
 
 RESULTS="$TMP/results.txt"