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>

lua/nuwiki/commands.lua

@@ -821,20 +821,44 @@ end
 
 local is_table_row = require('nuwiki.util').is_table_row
 
+-- 1-based byte positions of the cell-separator `|` characters in `s`. Pipes
+-- that are literal cell content are skipped: those inside `[[…]]` wikilinks,
+-- `{{…}}` transclusions, `` `…` `` inline code, and backslash-escaped `\|`.
+-- This keeps a `[[url|title]]` link in one cell instead of splitting on its
+-- internal pipe.
+local function cell_bar_positions(s)
+  local out = {}
+  local i = 1
+  local n = #s
+  while i <= n do
+    local c = s:sub(i, i)
+    if c == '\\' then
+      i = i + 2 -- skip the escaped char (e.g. `\|`)
+    elseif c == '`' then
+      local close = s:find('`', i + 1, true)
+      i = (close or n) + 1
+    elseif s:sub(i, i + 1) == '[[' then
+      local close = s:find(']]', i + 2, true)
+      i = close and close + 2 or n + 1
+    elseif s:sub(i, i + 1) == '{{' then
+      local close = s:find('}}', i + 2, true)
+      i = close and close + 2 or n + 1
+    elseif c == '|' then
+      table.insert(out, i)
+      i = i + 1
+    else
+      i = i + 1
+    end
+  end
+  return out
+end
+
 local function table_cell_starts(line)
   -- Returns 1-based byte positions of each `|` separator. Cell N spans
   -- (starts[N], starts[N+1]); placing the cursor at 0-based byte column
   -- `starts[i]` lands one position past the i-th `|` (the first space
   -- of the cell that the `|` opens).
-  local out = {}
-  local pos = 0
-  while true do
-    local bar = line:find('|', pos + 1, true)
-    if not bar then break end
-    table.insert(out, bar)
-    pos = bar
-  end
-  return out
+  return cell_bar_positions(line)
 end
 
 local function find_table_range(row)
@@ -856,15 +880,11 @@ local function parse_table_row(line)
   local body = line:sub(#indent + 1)
   local segments = {}
   local pos = 1
-  while true do
-    local bar = body:find('|', pos, true)
-    if not bar then
-      table.insert(segments, body:sub(pos))
-      break
-    end
+  for _, bar in ipairs(cell_bar_positions(body)) do
     table.insert(segments, body:sub(pos, bar - 1))
     pos = bar + 1
   end
+  table.insert(segments, body:sub(pos))
   -- Drop the empty piece before the opening `|` and the trailing piece
   -- after the closing `|`.
   if #segments > 0 and segments[1] == '' then table.remove(segments, 1) end