refactor(viml): extract shared heading_level/is_table_row/wiki_cfg; fix cap + spaceless

Mirrors the Lua util refactor. Pulls the copy-pasted VimL helpers into
autoload/nuwiki/util.vim and points the per-file s: stubs at it:

- heading_level (commands/folding/textobjects) — commands.vim's copy was
  missing the >6 level cap the others had (a 7+ `=` line returned 7). The
  unified version caps at 6 AND accepts spaceless headings (==Heading==),
  matching the server lexer + the Lua client (so fold fallback, text
  objects, and ]] navigation recognize spaceless headings too).
- is_table_row (commands/textobjects) — identical copies.
- wiki_cfg (commands/diary) — these had DRIFTED: commands.vim's included a
  `space` (links_space_char) key diary.vim's lacked. Unified to the superset
  so callers reading `.space` keep working; diary callers ignore the extra key.

Also refreshes the stale plugin/nuwiki.vim header ("all logic lives in the
Rust language server" → thin client; server is nuwiki-rs, downloaded).

Verified: 18-case heading battery in headless vim + full editor harness 10/10.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

autoload/nuwiki/commands.vim

@@ -468,15 +468,7 @@ endfunction
 " ===== Heading navigation (pure VimL) =====
 
 function! s:heading_level(line) abort
-  let l:lead = matchstr(a:line, '^\s*\zs=\+\ze\s')
+  return nuwiki#util#heading_level(a:line)
-  if l:lead ==# ''
-    return 0
-  endif
-  let l:trail = matchstr(a:line, '\s\zs=\+\ze\s*$')
-  if len(l:trail) != len(l:lead)
-    return 0
-  endif
-  return len(l:lead)
 endfunction
 
 function! s:current_heading_level() abort
@@ -593,21 +585,7 @@ endfunction
 " upstream g:vimwiki_list both work — and falls back to the scalar g:nuwiki_*
 " vars (single-wiki shorthand) and finally built-in defaults.
 function! s:wiki_cfg(n) abort
-  let l:wikis = nuwiki#config#wikis()
+  return nuwiki#util#wiki_cfg(a:n)
-  let l:w = (a:n >= 0 && a:n < len(l:wikis)) ? l:wikis[a:n] : {}
-  let l:root  = expand(get(l:w, 'root',
-        \ get(g:, 'nuwiki_wiki_root', '~/vimwiki')))
-  let l:ext   = get(l:w, 'file_extension',
-        \ get(g:, 'nuwiki_file_extension', '.wiki'))
-  if l:ext[0] !=# '.' | let l:ext = '.' . l:ext | endif
-  let l:idx       = get(l:w, 'index', 'index')
-  let l:diary_rel = get(l:w, 'diary_rel_path',
-        \ get(g:, 'nuwiki_diary_rel_path', 'diary'))
-  let l:diary_idx = get(l:w, 'diary_index', 'diary')
-  let l:space = get(l:w, 'links_space_char',
-        \ get(g:, 'nuwiki_links_space_char', ' '))
-  return { 'root': l:root, 'ext': l:ext, 'idx': l:idx,
-        \  'diary_rel': l:diary_rel, 'diary_idx': l:diary_idx, 'space': l:space }
 endfunction
 
 " Build the list of configured wikis as {name, root, ext, idx, diary_rel,
@@ -1178,7 +1156,7 @@ endfunction
 " matches `nuwiki-lsp/src/commands.rs::ops::render_aligned_table` (nuwiki-rs repo).
 
 function! s:is_table_row(line) abort
-  return a:line =~# '^\s*|.*|\s*$'
+  return nuwiki#util#is_table_row(a:line)
 endfunction
 
 function! s:table_cell_starts(line) abort

autoload/nuwiki/diary.vim

@@ -106,17 +106,5 @@ endfunction
 " nuwiki#config#wikis() so g:nuwiki_wikis AND an upstream g:vimwiki_list both
 " work, falling back to the scalar g:nuwiki_* single-wiki shorthand.
 function! s:wiki_cfg(n) abort
-  let l:wikis = nuwiki#config#wikis()
+  return nuwiki#util#wiki_cfg(a:n)
-  let l:w = (a:n >= 0 && a:n < len(l:wikis)) ? l:wikis[a:n] : {}
-  let l:root  = expand(get(l:w, 'root',
-        \ get(g:, 'nuwiki_wiki_root', '~/vimwiki')))
-  let l:ext   = get(l:w, 'file_extension',
-        \ get(g:, 'nuwiki_file_extension', '.wiki'))
-  if l:ext[0] !=# '.' | let l:ext = '.' . l:ext | endif
-  let l:idx       = get(l:w, 'index', 'index')
-  let l:diary_rel = get(l:w, 'diary_rel_path',
-        \ get(g:, 'nuwiki_diary_rel_path', 'diary'))
-  let l:diary_idx = get(l:w, 'diary_index', 'diary')
-  return { 'root': l:root, 'ext': l:ext, 'idx': l:idx,
-        \  'diary_rel': l:diary_rel, 'diary_idx': l:diary_idx }
 endfunction

autoload/nuwiki/folding.vim

@@ -13,15 +13,7 @@
 " end of buffer).
 
 function! s:heading_level(line) abort
-  let l:lead = matchstr(a:line, '^\s*\zs=\+\ze\s')
+  return nuwiki#util#heading_level(a:line)
-  if empty(l:lead) | return 0 | endif
-  let l:lvl = strlen(l:lead)
-  if l:lvl > 6 | return 0 | endif
-  let l:trail = matchstr(a:line, '\s\zs=\+\ze\s*$')
-  if empty(l:trail) || strlen(l:trail) != l:lvl
-    return 0
-  endif
-  return l:lvl
 endfunction
 
 function! nuwiki#folding#expr() abort

autoload/nuwiki/textobjects.vim

@@ -24,15 +24,7 @@
 " ===== Heading helpers =====
 
 function! s:heading_level(line) abort
-  let l:lead = matchstr(a:line, '^\s*\zs=\+\ze\s')
+  return nuwiki#util#heading_level(a:line)
-  if empty(l:lead) | return 0 | endif
-  let l:lvl = strlen(l:lead)
-  if l:lvl > 6 | return 0 | endif
-  let l:trail = matchstr(a:line, '\s\zs=\+\ze\s*$')
-  if empty(l:trail) || strlen(l:trail) != l:lvl
-    return 0
-  endif
-  return l:lvl
 endfunction
 
 " Returns `[start, end]` line numbers, or `[]` if no heading found.
@@ -130,7 +122,7 @@ endfunction
 " ===== Table cell / column =====
 
 function! s:is_table_row(line) abort
-  return a:line =~# '^\s*|.*|\s*$'
+  return nuwiki#util#is_table_row(a:line)
 endfunction
 
 " Returns a list of `[start_col, end_col]` byte positions (1-based,

autoload/nuwiki/util.vim

@@ -0,0 +1,56 @@
+" autoload/nuwiki/util.vim — small shared helpers used across the VimL client
+" layers (commands, folding, textobjects, diary). Keeps the formerly
+" copy-pasted heading / table-row / wiki-config logic in one place. Mirrors
+" lua/nuwiki/util.lua so both clients behave identically.
+
+" Heading level of `line` (1-6), or 0 when it isn't a heading. Mirrors the
+" server lexer: balanced leading/trailing runs of `=` around a non-empty
+" title, capped at level 6. Accepts both the spaced (`== H ==`) and spaceless
+" (`==H==`) forms, matching vimwiki.
+function! nuwiki#util#heading_level(line) abort
+  let l:lead = matchstr(a:line, '^\s*\zs=\+')
+  if empty(l:lead)
+    return 0
+  endif
+  let l:lvl = strlen(l:lead)
+  if l:lvl > 6
+    return 0
+  endif
+  " Same-length trailing run of `=` at end of line (after optional trailing ws).
+  let l:trail = matchstr(a:line, '=\+\ze\s*$')
+  if empty(l:trail) || strlen(l:trail) != l:lvl
+    return 0
+  endif
+  " Non-empty title between the runs (rules out marker-only lines like
+  " `======`). `.\{-}` is non-greedy so the `=\+` runs keep their length.
+  let l:body = matchstr(a:line, '^\s*=\+\zs.\{-}\ze=\+\s*$')
+  if l:body =~# '^\s*$'
+    return 0
+  endif
+  return l:lvl
+endfunction
+
+" True when `line` looks like a table row (`| … |`).
+function! nuwiki#util#is_table_row(line) abort
+  return a:line =~# '^\s*|.*|\s*$'
+endfunction
+
+" Resolve the config dict for wiki #n (0-based), falling back to the scalar
+" g:nuwiki_* globals. Returns root/ext/idx/diary_rel/diary_idx/space.
+function! nuwiki#util#wiki_cfg(n) abort
+  let l:wikis = nuwiki#config#wikis()
+  let l:w = (a:n >= 0 && a:n < len(l:wikis)) ? l:wikis[a:n] : {}
+  let l:root  = expand(get(l:w, 'root',
+        \ get(g:, 'nuwiki_wiki_root', '~/vimwiki')))
+  let l:ext   = get(l:w, 'file_extension',
+        \ get(g:, 'nuwiki_file_extension', '.wiki'))
+  if l:ext[0] !=# '.' | let l:ext = '.' . l:ext | endif
+  let l:idx       = get(l:w, 'index', 'index')
+  let l:diary_rel = get(l:w, 'diary_rel_path',
+        \ get(g:, 'nuwiki_diary_rel_path', 'diary'))
+  let l:diary_idx = get(l:w, 'diary_index', 'diary')
+  let l:space = get(l:w, 'links_space_char',
+        \ get(g:, 'nuwiki_links_space_char', ' '))
+  return { 'root': l:root, 'ext': l:ext, 'idx': l:idx,
+        \  'diary_rel': l:diary_rel, 'diary_idx': l:diary_idx, 'space': l:space }
+endfunction

plugin/nuwiki.vim

@@ -4,8 +4,9 @@
 " their config (lazy.nvim does this automatically through `opts`). On Vim
 " we start the LSP client when a vimwiki buffer is loaded.
 "
-" This file contains wiring only — all logic lives in
+" This file contains wiring only. The editor layers (VimL + Lua) are thin
-" the Rust language server.
+" clients; the heavy lifting is done by the nuwiki-ls language server, which
+" is built from the separate nuwiki-rs repo and downloaded at install time.
 
 if exists('g:loaded_nuwiki')
   finish