feat(parity): P3 quick-wins — ShowVersion, gLH/gLL/gLR, Search/Align nargs

Closes four low-risk P3 parity items (gap doc updated):

- VimwikiShowVersion / NuwikiShowVersion: new global command (both clients)
  echoing g:nuwiki_version (0.1.0) + the host editor, via
  nuwiki#commands#show_version / commands.show_version.

- gLH / gLL / gLR: upstream's case-variant aliases of gLh/gLl/gLr (dedent /
  indent whole item, renumber all lists) added in both clients.

- VimwikiSearch / VWS: -nargs=1 -> -nargs=* (Vim + Neovim), so a multi-word
  search no longer raises E488 and an empty invocation reuses the last search
  pattern. (The lvimgrep-vs-vimwiki-engine difference stays open.)

- VimwikiTableAlignQ / AlignW / NuwikiTableAlign: bare -> -nargs=?, so
  `:VimwikiTableAlignQ 2` no longer raises E488 (optional column arg is
  accepted-and-ignored; the gqq-align vs gww-align-without-resize split
  stays open).

Docs (doc/nuwiki.txt + README) updated for the command and the aliases.
Tests: surface.{Vimwiki,Nuwiki}ShowVersion, map[n].gL{H,L,R} (both
harnesses), cmd.search_and_tablealign_nargs (vim). Neovim 291, Vim
282/18/21 pass.

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

doc/nuwiki.txt

@@ -349,6 +349,11 @@ Wiki / navigation ~
     Pick a wiki from a list (multi-wiki only). Uses |vim.ui.select| on
     Neovim, |inputlist()| on Vim.
 
+                                                       *:NuwikiShowVersion*
+:NuwikiShowVersion
+    Echo the nuwiki version (`g:nuwiki_version`) and the host editor.
+    Also available as `:VimwikiShowVersion`.
+
                                                                *:NuwikiGoto*
 :NuwikiGoto {page}
     Open `{page}.wiki` by name.
@@ -611,10 +616,10 @@ Lists (normal mode) ~
   gnt        Jump to the next unfinished task.
   glh        Dedent the current list item.
   gll        Indent the current list item.
-  gLh        Dedent the item including its sublist.
-  gLl        Indent the item including its sublist.
+  gLh        Dedent the item including its sublist.  (alias: gLH)
+  gLl        Indent the item including its sublist.  (alias: gLL)
   glr        Renumber the current ordered list.
-  gLr        Renumber every ordered list in the buffer.
+  gLr        Renumber every ordered list in the buffer.  (alias: gLR)
   gl<sym>    Set the current item's marker to <sym>, where <sym> is one
              of `-` `*` `#` `1` (1.) `i` (i)) `I` (I)) `a` (a)) `A` (A)).
              For `1)` use `:NuwikiChangeSymbol 1)` (no single-key form).