feat(parity): close the entire P3 Commands section

All six remaining command gaps (client-side; no server change):

- VimwikiRenameFile: bare -> -nargs=? (arg accepted-ignored; rename still
  delegates to the LSP rename prompt). No more E488.

- VimwikiVar / NuwikiVar: get/set the client config (upstream vimwiki#vars#cmd).
  No arg prints config (Vim: g:nuwiki_*; Neovim: resolved setup() opts), one arg
  gets a key, two+ sets it. Global command, both clients.

- VimwikiReturn / NuwikiReturn: command form of the smart <CR> continuation —
  enters insert at EOL and fires the <CR> mapping (return_cmd / vimwiki_return).
  Upstream's mode-flag args accepted but unused.

- VimwikiTableAlignQ vs AlignW: corrected — upstream's gqq/gww are identical on
  a table; the only difference is the non-table fallback (native `normal! gqq`
  vs `gww`). New table_align_or_cmd(cmd) aligns on a table row, else runs
  `normal! <cmd>`. Q/gqq/gq1 -> gqq; W/gww/gw1 -> gww; NuwikiTableAlign -> gqq.

- VimwikiSearch / VWS: scope the lvimgrep to the current wiki's root (resolved
  client-side) over <root>/**/*<ext>, not CWD `**`; empty pattern reuses the
  last search. Both clients.

- VimwikiIndex family: add global Vimwiki/NuwikiIndex + TabIndex entry points
  (plugin/nuwiki.vim + init.lua _setup_global_commands, with -count), so a wiki
  opens from any buffer. Buffer-local copies still shadow inside wiki buffers.

Tests: surface.{Vimwiki,Nuwiki}{Return,Var}, cmd.VimwikiVar_sets_*,
cmd.global_entry_points (both harnesses). Docs (README + doc/nuwiki.txt) and the
gap doc updated. Neovim 299, Vim 291/18/21 pass.

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

README.md

@@ -442,7 +442,10 @@ available on both the Neovim and plain-Vim paths.
 | `:NuwikiNextLink` / `:NuwikiPrevLink` | `:VimwikiNextLink` / `:VimwikiPrevLink` | Jump to the next / previous wikilink |
 | `:NuwikiBaddLink` | `:VimwikiBaddLink` | Add the link target under the cursor to the buffer list |
 | `:NuwikiNormalizeLink` | `:VimwikiNormalizeLink` | Wrap the word / visual selection under the cursor as a wikilink |
-| — | `:VimwikiSearch {pat}` (`:VWS`) | `:lvimgrep` `{pat}` across every page |
+| — | `:VimwikiSearch {pat}` (`:VWS`) | `:lvimgrep` `{pat}` across the current wiki's pages (empty `{pat}` reuses the last search) |
+| `:NuwikiVar` | `:VimwikiVar [key [val]]` | Get/set nuwiki client config |
+| `:NuwikiReturn` | `:VimwikiReturn` | Command form of the smart `<CR>` list/table continuation |
+| `:NuwikiShowVersion` | `:VimwikiShowVersion` | Print the nuwiki version + host editor |
 
 **Diary**