fix(lsp): add coc.nvim dispatch path to all Vim-side LSP calls

Commands were hardwired to vim-lsp (lsp#send_request, :LspDefinition,
:LspReferences, :LspRename). Users running coc.nvim got "vim-lsp not
loaded" on every command despite the plugin correctly detecting coc.

Changes:

autoload/nuwiki/commands.vim
- Add s:has_coc() (checks CocActionAsync exists)
- Add s:coc_wrap() adapter — converts coc's (err, result) callback into
  the vim-lsp notification shape {response:{result:…}} so all existing
  on_notification handlers work unchanged
- s:exec(): try vim-lsp first, fall back to CocActionAsync('runCommand',
  …) with arguments spread as positional params, then error if neither
- Add s:jump_definition() helper — :LspDefinition vs CocActionAsync
- Add nuwiki#commands#backlinks() — :LspReferences vs CocActionAsync
- badd_link(): coc path uses CocAction('getDefinition') to resolve the
  target URI without navigating
- follow_link_or_create(): replace inline :LspDefinition checks with
  s:jump_definition()
- rename_file(): :LspRename vs CocActionAsync('rename')

ftplugin/vimwiki.vim
- VimwikiFollowLink / NuwikiFollowLink: dispatch through
  nuwiki#commands#follow_link_or_create() instead of :LspDefinition
- VimwikiBacklinks / NuwikiBacklinks / VWB: dispatch through
  nuwiki#commands#backlinks() instead of :LspReferences

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

autoload/nuwiki/commands.vim

@@ -24,21 +24,75 @@ function! s:has_vimlsp() abort
   return exists('*lsp#send_request')
 endfunction
 
-function! s:exec(command, arguments, ...) abort
-  if !s:has_vimlsp()
+function! s:has_coc() abort
+  return exists('*CocActionAsync')
+endfunction
+
+" Adapt a coc.nvim (err, result) callback into the vim-lsp notification
+" shape that existing on_notification handlers expect.
+function! s:coc_wrap(upstream, err, result) abort
+  if a:err isnot v:null && a:err !=# 0
     echohl ErrorMsg
-    echom 'nuwiki: vim-lsp not loaded; cannot run ' . a:command
+    echom 'nuwiki: ' . (type(a:err) == type('') ? a:err : string(a:err))
     echohl None
     return
   endif
-  let l:opts = {
-        \ 'method': 'workspace/executeCommand',
-        \ 'params': { 'command': a:command, 'arguments': a:arguments },
-        \ }
-  if a:0 >= 1
-    let l:opts['on_notification'] = a:1
+  call a:upstream({ 'response': { 'result': a:result } })
+endfunction
+
+function! s:exec(command, arguments, ...) abort
+  if s:has_vimlsp()
+    let l:opts = {
+          \ 'method': 'workspace/executeCommand',
+          \ 'params': { 'command': a:command, 'arguments': a:arguments },
+          \ }
+    if a:0 >= 1
+      let l:opts['on_notification'] = a:1
+    endif
+    call lsp#send_request(s:server, l:opts)
+    return
+  endif
+
+  if s:has_coc()
+    " CocActionAsync('runCommand', cmdid, arg1, arg2, …, callback)
+    " The arguments list is spread as individual positional args.
+    let l:args = ['runCommand', a:command] + a:arguments
+    if a:0 >= 1
+      call add(l:args, function('s:coc_wrap', [a:1]))
+    endif
+    call call('CocActionAsync', l:args)
+    return
+  endif
+
+  echohl ErrorMsg
+  echom 'nuwiki: no supported LSP client. Install vim-lsp or configure coc.nvim.'
+  echohl None
+endfunction
+
+" Shared jump-to-definition helper used by follow_link* and the ftplugin.
+function! s:jump_definition() abort
+  if exists(':LspDefinition') == 2
+    LspDefinition
+  elseif s:has_coc()
+    call CocActionAsync('jumpDefinition')
+  else
+    echohl WarningMsg
+    echom 'nuwiki: no LSP client available for jump-to-definition'
+    echohl None
+  endif
+endfunction
+
+" Shared references helper used by the ftplugin.
+function! nuwiki#commands#backlinks() abort
+  if exists(':LspReferences') == 2
+    LspReferences
+  elseif s:has_coc()
+    call CocActionAsync('references')
+  else
+    echohl WarningMsg
+    echom 'nuwiki: no LSP client available for references'
+    echohl None
   endif
-  call lsp#send_request(s:server, l:opts)
 endfunction
 
 function! s:open_uri_from(response, ...) abort
@@ -105,15 +159,27 @@ endfunction
 " `:VimwikiBaddLink` — add the link target file to the buffer list
 " without focus. Routes through vim-lsp's textDocument/definition.
 function! nuwiki#commands#badd_link() abort
-  if !s:has_vimlsp()
-    echohl ErrorMsg | echom 'nuwiki: vim-lsp not loaded' | echohl None
+  if s:has_vimlsp()
+    call lsp#send_request(s:server, {
+          \ 'method': 'textDocument/definition',
+          \ 'params': s:cursor_position(),
+          \ 'on_notification': function('s:badd_from_response'),
+          \ })
     return
   endif
-  call lsp#send_request(s:server, {
-        \ 'method': 'textDocument/definition',
-        \ 'params': s:cursor_position(),
-        \ 'on_notification': function('s:badd_from_response'),
-        \ })
+  if s:has_coc()
+    let l:locs = CocAction('getDefinition')
+    if type(l:locs) == type([]) && !empty(l:locs)
+      let l:uri = get(l:locs[0], 'uri', get(l:locs[0], 'targetUri', ''))
+      if !empty(l:uri)
+        let l:path = substitute(l:uri, '^file://', '', '')
+        execute 'badd ' . fnameescape(l:path)
+        echom 'nuwiki: added ' . l:path
+      endif
+    endif
+    return
+  endif
+  echohl ErrorMsg | echom 'nuwiki: no supported LSP client for badd_link' | echohl None
 endfunction
 
 function! s:badd_from_response(notification) abort
@@ -188,23 +254,15 @@ endfunction
 "   3. Press inside an existing `[[…]]` follows immediately.
 function! nuwiki#commands#follow_link_or_create() abort
   if s:cursor_inside_wikilink()
-    if exists(':LspDefinition') == 2
-      LspDefinition
-    else
-      echohl WarningMsg
-      echom 'nuwiki: :LspDefinition unavailable; install vim-lsp'
-      echohl None
-    endif
+    call s:jump_definition()
     return
   endif
   if s:wrap_cword_as_wikilink()
     " Wrapped — wait for the user's second <CR> to follow.
     return
   endif
-  " Nothing to wrap — fall through.
-  if exists(':LspDefinition') == 2
-    LspDefinition
-  endif
+  " Nothing to wrap — fall through to plain definition.
+  call s:jump_definition()
 endfunction
 
 " Pure-VimL bullet-continuation for `o` / `O` — mirrors the Lua side
@@ -535,11 +593,13 @@ function! nuwiki#commands#delete_file() abort
 endfunction
 
 function! nuwiki#commands#rename_file() abort
-  if exists('*lsp#rename')
+  if exists(':LspRename') == 2
     LspRename
+  elseif s:has_coc()
+    call CocActionAsync('rename')
   else
     echohl WarningMsg
-    echom 'nuwiki: :LspRename unavailable; install vim-lsp'
+    echom 'nuwiki: no LSP client available for rename'
     echohl None
   endif
 endfunction