fix(search): graceful no-match + NuwikiSearch alias (re-audit follow-up)

Re-audit of the just-landed command work found one real bug I introduced
and a convention gap:

- VimwikiSearch / VWS raised a raw E480 on a no-match search; upstream
  reports it gracefully. Both clients now catch it (try/catch in Vim,
  pcall in Neovim) and emit "nuwiki: no match for <pat>".

- Added a NuwikiSearch alias alongside VimwikiSearch/VWS (every other
  command carries a Nuwiki* form).

Gap-doc note corrected: nuwiki's search populates + opens the location
list (shows all matches) where upstream jumps to the first match — logged
as a minor presentation divergence rather than claiming exact parity.

Config + mappings re-audits came back clean (no new gaps, no regressions;
table-mapping rewire verified non-recursive, gLH/gLL/gLR present).

Tests: cmd.VimwikiSearch_no_match_graceful, surface.{Vimwiki,Nuwiki}Search.
Neovim 301, Vim 294/18/21 pass.

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

development/tests/test-keymaps.lua

@@ -139,7 +139,7 @@ vim.defer_fn(function()
     'RebuildTags', '2HTML', '2HTMLBrowse', 'All2HTML', 'Rss',
     'NormalizeLink', 'RenumberList', 'RenumberAllLists',
     'ListToggle', 'IncrementListItem', 'DecrementListItem',
-    'CatUrl', 'ShowVersion', 'Return', 'Var',
+    'CatUrl', 'ShowVersion', 'Return', 'Var', 'Search',
   }
   for _, suffix in ipairs(both_forms) do
     for _, prefix in ipairs({ 'Nuwiki', 'Vimwiki' }) do