parity(2): insert-mode list bindings (<C-D>/<C-T>/<C-L><C-?>)

Match upstream vimwiki's insert-mode list editing:
  <C-D>      list_change_level(-1)   dedent current item
  <C-T>      list_change_level(+1)   indent current item
  <C-L><C-J> list_cycle_symbol(+1)   cycle marker forward
  <C-L><C-K> list_cycle_symbol(-1)   cycle marker backward
  <C-L><C-M> list_toggle_or_add_chk  toggle if has checkbox, else add `[ ]`

Cycle order matches vimwiki's canonical run:
  - → * → # → 1. → 1) → a) → A) → i) → I) → (wrap)

Both Lua and VimL paths wired. Lua callbacks fire directly (no `<C-o>`
dance) since list_change_level / changeSymbol mutate the buffer via
the LSP applyEdit pipeline, which works cleanly in insert mode. VimL
keeps the `<C-o>:call …<CR>` idiom since that's the standard there.

Harness adds 5 cases covering the new insert-mode bindings plus one
direct LSP roundtrip for changeSymbol — surfaced a long-standing
stale-binary footgun in test-keymaps.sh (rebuilt only when bin was
missing; now rebuilds every run since incremental cargo is fast).
Harness also captures server log_messages and dumps them on failure
so future swallowed-error bugs (Err → log + Ok(None)) are visible.

Gates: 421 Rust / 25 Neovim / 12 Vim.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

autoload/nuwiki/commands.vim

@@ -551,6 +551,47 @@ function! nuwiki#commands#list_change_lvl(...) abort
   let l:delta = (l:dir ==# 'increase' || l:dir ==# 'indent') ? 1 : -1
   call nuwiki#commands#list_change_level(l:delta, 0)
 endfunction
+
+" Cycle the list marker through vimwiki's canonical order.
+let s:symbol_order = ['-', '*', '#', '1.', '1)', 'a)', 'A)', 'i)', 'I)']
+
+function! s:detect_symbol() abort
+  let l:line = getline('.')
+  let l:m = matchlist(l:line, '^\s*\([-*#]\)\s')
+  if !empty(l:m) | return l:m[1] | endif
+  let l:m = matchlist(l:line, '^\s*\d\+\([.)]\)\s')
+  if !empty(l:m) | return '1' . l:m[1] | endif
+  if l:line =~# '^\s*[ivxlcdm]\+)\s' | return 'i)' | endif
+  if l:line =~# '^\s*[IVXLCDM]\+)\s' | return 'I)' | endif
+  if l:line =~# '^\s*[a-z]\+)\s'     | return 'a)' | endif
+  if l:line =~# '^\s*[A-Z]\+)\s'     | return 'A)' | endif
+  return ''
+endfunction
+
+function! nuwiki#commands#list_cycle_symbol(direction) abort
+  let l:cur = s:detect_symbol()
+  if l:cur ==# '' | return | endif
+  let l:idx = index(s:symbol_order, l:cur)
+  if l:idx < 0 | return | endif
+  let l:n = (l:idx + a:direction) % len(s:symbol_order)
+  if l:n < 0 | let l:n += len(s:symbol_order) | endif
+  call nuwiki#commands#list_change_symbol(s:symbol_order[l:n], 0)
+endfunction
+
+function! nuwiki#commands#list_toggle_or_add_checkbox() abort
+  let l:line = getline('.')
+  if l:line =~# '^\s*[-*#]\s\+\[[ xXoO.\-]\]' || l:line =~# '^\s*\w\+[.)]\s\+\[[ xXoO.\-]\]'
+    call nuwiki#commands#toggle_list_item()
+    return
+  endif
+  let l:end = matchend(l:line, '^\s*[-*#] ')
+  if l:end < 0
+    let l:end = matchend(l:line, '^\s*\w\+[.)] ')
+  endif
+  if l:end < 0 | return | endif
+  let l:new = strpart(l:line, 0, l:end) . '[ ] ' . strpart(l:line, l:end)
+  call setline('.', l:new)
+endfunction
 " §13.1 Cluster B — table rewriters.
 
 function! nuwiki#commands#table_insert(...) abort