fix(tables): don't split a cell on a | inside a link/code/escape

Table auto-alignment scanned for cell separators with a naive find('|'),
so a cell containing a vimwiki link `[[url|title]]` was split at the link's
internal pipe — mangling both the link (`[[url` / `title]]`) and the table
(a phantom extra column). Same bug in both the Lua (Neovim) and VimL (Vim)
table code, in both table_cell_starts and parse_table_row.

Add a shared cell-separator scanner (cell_bar_positions) that treats `|` as
literal — not a separator — when it's inside `[[…]]` wikilinks, `{{…}}`
transclusions, `` `…` `` inline code, or backslash-escaped (`\|`), matching
vimwiki. Both scan functions in each client now use it.

Regression tests added on both clients (cr.table_link_cell_pipe_not_a_separator);
full harness green (Neovim 308, Vim 302).

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

autoload/nuwiki/commands.vim

@@ -1159,19 +1159,44 @@ function! s:is_table_row(line) abort
   return nuwiki#util#is_table_row(a:line)
 endfunction
 
+" 0-based byte offsets of the cell-separator `|` in `s`. Pipes that are literal
+" cell content are skipped: those inside `[[…]]` wikilinks, `{{…}}`
+" transclusions, `` `…` `` inline code, and backslash-escaped `\|`. Byte-based
+" (strpart/stridx) to match the rest of the table code. Keeps a `[[url|title]]`
+" link in one cell instead of splitting on its internal pipe.
+function! s:cell_bar_positions(s) abort
+  let l:out = []
+  let l:i = 0
+  let l:n = strlen(a:s)
+  while l:i < l:n
+    let l:c = strpart(a:s, l:i, 1)
+    let l:two = strpart(a:s, l:i, 2)
+    if l:c ==# '\'
+      let l:i += 2
+    elseif l:c ==# '`'
+      let l:close = stridx(a:s, '`', l:i + 1)
+      let l:i = l:close < 0 ? l:n : l:close + 1
+    elseif l:two ==# '[['
+      let l:close = stridx(a:s, ']]', l:i + 2)
+      let l:i = l:close < 0 ? l:n : l:close + 2
+    elseif l:two ==# '{{'
+      let l:close = stridx(a:s, '}}', l:i + 2)
+      let l:i = l:close < 0 ? l:n : l:close + 2
+    elseif l:c ==# '|'
+      call add(l:out, l:i)
+      let l:i += 1
+    else
+      let l:i += 1
+    endif
+  endwhile
+  return l:out
+endfunction
+
 function! s:table_cell_starts(line) abort
   " 1-based byte positions of each `|`. Cursor lands one past pipe N at
   " 1-based byte (starts[N] + 1) — that's the first space inside the
   " cell the pipe opens.
-  let l:out = []
-  let l:pos = 0
-  while 1
-    let l:bar = stridx(a:line, '|', l:pos)
-    if l:bar < 0 | break | endif
-    call add(l:out, l:bar + 1)
-    let l:pos = l:bar + 1
-  endwhile
-  return l:out
+  return map(s:cell_bar_positions(a:line), 'v:val + 1')
 endfunction
 
 function! s:find_table_range(row) abort
@@ -1192,15 +1217,11 @@ function! s:parse_table_row(line) abort
   let l:body = strpart(a:line, len(l:indent))
   let l:segments = []
   let l:pos = 0
-  while 1
-    let l:bar = stridx(l:body, '|', l:pos)
-    if l:bar < 0
-      call add(l:segments, strpart(l:body, l:pos))
-      break
-    endif
+  for l:bar in s:cell_bar_positions(l:body)
     call add(l:segments, strpart(l:body, l:pos, l:bar - l:pos))
     let l:pos = l:bar + 1
-  endwhile
+  endfor
+  call add(l:segments, strpart(l:body, l:pos))
   " Drop the empty piece before the opening `|` and the trailing piece
   " after the closing `|`.
   if len(l:segments) > 0 && l:segments[0] ==# ''