feat: real range/bang/visual handling for the deferred command gaps

Implements the four items previously left as "needs handler work" — all
fully wired, not cosmetic.

- ToggleListItem / IncrementListItem / DecrementListItem are now -range
  (both clients). The client loops the per-line op over [<line1>,<line2>]
  (toggle_list_item_range / list_cycle_symbol_range). The server's edits are
  version-less single-line WorkspaceEdits, so each line applies independently
  — no server protocol change. `:'<,'>VimwikiToggleListItem` toggles the whole
  selection.
- VimwikiRebuildTags gains -bang: `:…RebuildTags!` passes { all: true } and
  the server (tags_rebuild) re-indexes every configured wiki via
  wikis_snapshot(), not just the current one.
- VimwikiNormalizeLink is -nargs=?: with `1` (upstream's visual flag; the
  x-mode `+` mapping now passes it) it wraps the '< / '> selection as
  [[selection]] (new wrap_visual_as_wikilink in both clients).
- VimwikiCheckLinks is -range: a ranged invocation filters the broken-link
  report to the current buffer's selected lines (client-side filter in
  results_to_qf / check_links).

Tests: cmd.toggle_list_item_range + cmd.normalize_link_visual_wraps_selection
(test-keymaps.lua), normalize.visual_wraps_selection (test-keymaps-vim.vim).
README + doc/nuwiki.txt + gap doc updated. fmt/clippy clean; nvim 274,
vim 266+18, all Rust tests + config-parity green.

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

development/tests/test-keymaps.lua

@@ -792,6 +792,34 @@ vim.defer_fn(function()
     end
   end)
 
+  -- ===== Visual-range list commands + normalize-visual (regression) =====
+  -- :N,MVimwikiToggleListItem toggles every checkbox in the range (server,
+  -- one request per line; wait for the edits to land).
+  tobj_case('cmd.toggle_list_item_range', function()
+    set_buf({ '- [ ] a', '- [ ] b', '- [ ] c' })
+    vim.cmd('1,3VimwikiToggleListItem')
+    local done = vim.wait(2000, function()
+      for _, l in ipairs(vim.api.nvim_buf_get_lines(0, 0, -1, false)) do
+        if not l:match('%[[xX]%]') then return false end
+      end
+      return true
+    end, 30)
+    if not done then
+      error('range toggle incomplete: ' .. vim.inspect(vim.api.nvim_buf_get_lines(0, 0, -1, false)))
+    end
+  end)
+  -- `:VimwikiNormalizeLink 1` (the arg is upstream's visual flag; the command
+  -- is -nargs=? not -range, so no `'<,'>`) wraps the last visual selection.
+  tobj_case('cmd.normalize_link_visual_wraps_selection', function()
+    set_buf({ 'one two three' })
+    vim.cmd('normal! 0wviw\27') -- select 'two', leave visual (sets '<,'> marks)
+    vim.cmd('VimwikiNormalizeLink 1')
+    local got = vim.api.nvim_get_current_line()
+    if got ~= 'one [[two]] three' then
+      error('visual normalize did not wrap selection: ' .. got)
+    end
+  end)
+
   -- ===== Wiki picker (config-driven, no LSP) =====
   -- The picker must build its list from config so it works from any buffer
   -- before the server attaches.