fix(client): VimwikiColorize accepts a range (no more E481 on selection)

Selecting text and running :VimwikiColorize {color} raised
"E481: No range allowed" — Vim prepends '<,'> to the command when invoked
from a visual selection, but the command was defined without -range.

All four colorize command defs (Vim + Neovim, Vimwiki* + Nuwiki*) are now
-range and forward the range count to the handler. A ranged (visual)
invocation wraps the '< / '> selection; a bare invocation wraps the cword.
The x-mode <Leader>wc mapping passes the visual flag explicitly.

The Vim-branch colorize() gained selection support (it was cword-only),
matching the Neovim branch, so both clients wrap a visual selection
identically. visual_selection_range() (Lua) no longer gates on
vim.fn.visualmode() — the explicit visual flag now carries that intent, and
the marks check guards unset selections.

Tests: cmd.Colorize_range_wraps_selection (nvim) and
colorize.{command_wraps_cword,visual_wraps_selection,ranged_command_no_error}
(vim). nvim 268, vim 257+18, all green.

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

lua/nuwiki/commands.lua

@@ -951,9 +951,11 @@ end
 --- the template is `<span style="color:%c">%s</span>` with `%c`
 --- replaced by the user-supplied colour and `%s` by the wrapped text.
 --- Pure-Lua; no server roundtrip needed.
+-- Read the last visual selection from the `'<`/`'>` marks. Only meaningful
+-- when the caller knows it's acting on a selection (colorize's `visual` flag);
+-- we deliberately don't gate on vim.fn.visualmode() here since that reflects
+-- session state, not whether the marks are the selection we want right now.
 local function visual_selection_range()
-  local mode = vim.fn.visualmode()
-  if mode == '' then return nil end
   local s = vim.api.nvim_buf_get_mark(0, '<')
   local e = vim.api.nvim_buf_get_mark(0, '>')
   if s[1] == 0 or e[1] == 0 then return nil end