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>

README.md

@@ -429,10 +429,10 @@ available on both the Neovim and plain-Vim paths.
 | Nuwiki | Vimwiki | Action |
 |---|---|---|
 | `:NuwikiNextTask` | `:VimwikiNextTask` | Jump to the next unfinished task |
-| `:NuwikiToggleListItem` | `:VimwikiToggleListItem` | Toggle the checkbox under the cursor |
+| `:NuwikiToggleListItem` | `:VimwikiToggleListItem` | Toggle the checkbox under the cursor (`-range`: every item in the selection) |
 | `:NuwikiToggleRejected` | `:VimwikiToggleRejectedListItem` | Toggle the rejected marker `[-]` |
 | `:NuwikiListToggle` | `:VimwikiListToggle` | Toggle a checkbox on the current item (adds `[ ]` if none) |
-| `:NuwikiIncrementListItem` / `:NuwikiDecrementListItem` | `:VimwikiIncrementListItem` / `:VimwikiDecrementListItem` | Cycle the list marker to the next / previous symbol |
+| `:NuwikiIncrementListItem` / `:NuwikiDecrementListItem` | `:VimwikiIncrementListItem` / `:VimwikiDecrementListItem` | Cycle the list marker to the next / previous symbol (`-range`: every item in the selection) |
 | `:NuwikiChangeSymbol {sym}` | `:VimwikiChangeSymbolTo {sym}` (`:VimwikiListChangeSymbolI`) | Set the current item's marker to `{sym}` |
 | `:NuwikiChangeSymbolInList {sym}` | `:VimwikiChangeSymbolInListTo {sym}` | Set every item in the list to `{sym}` |
 | `:NuwikiRemoveDone[!]` | `:VimwikiRemoveDone[!]` | Remove every completed item from the current list; with `!`, from the whole buffer |
@@ -451,9 +451,9 @@ available on both the Neovim and plain-Vim paths.
 |---|---|---|
 | `:NuwikiTOC` | `:VimwikiTOC` | Generate / refresh the table of contents on the current page |
 | `:NuwikiGenerateLinks` | `:VimwikiGenerateLinks` | Insert a flat list of every page in the wiki |
-| `:NuwikiCheckLinks` | `:VimwikiCheckLinks` | Send broken links to the quickfix list |
+| `:NuwikiCheckLinks` | `:VimwikiCheckLinks` | Send broken links to the quickfix list (`-range`: limit to the current buffer's selected lines) |
 | `:NuwikiFindOrphans` | `:VimwikiFindOrphans` | List pages with no incoming links in the quickfix list |
-| `:NuwikiRebuildTags` | `:VimwikiRebuildTags` | Force a full workspace re-index |
+| `:NuwikiRebuildTags[!]` | `:VimwikiRebuildTags[!]` | Re-index the current wiki; `!` re-indexes every configured wiki |
 | `:NuwikiSearchTags {tag}` | `:VimwikiSearchTags {tag}` | Quickfix listing every occurrence of `:tag:` |
 | `:NuwikiGenerateTagLinks [tag]` | `:VimwikiGenerateTagLinks [tag]` (`:VimwikiGenerateTags`) | Insert a section linking every page that has `<tag>` |
 | `:NuwikiColorize {color}` | `:VimwikiColorize {color}` | Wrap the word / visual selection in a coloured `<span>` |