refactor(lua): extract shared heading_level/is_table_row; dedup wiki_list in search

Pulls the duplicated heading_level (keymaps/folding/textobjects) and
is_table_row (commands/textobjects) helpers into lua/nuwiki/util.lua. The
copies had drifted — only folding capped level >6 and only commands
nil-guarded is_table_row; the unified versions keep both (cap + nil-safe),
which also aligns the keymap/textobject paths with the server's level cap.
search() now resolves config.wiki_list() once instead of twice.

No behaviour change beyond the >6 cap now applying everywhere. Full editor
harness green (10/10).

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

lua/nuwiki/commands.lua

@@ -331,8 +331,9 @@ function M.search(args)
   end
   local config = require('nuwiki.config')
   local file = vim.fn.expand('%:p')
+  local wikis = config.wiki_list()
   local root, ext = '', '.wiki'
-  for _, w in ipairs(config.wiki_list()) do
+  for _, w in ipairs(wikis) do
     local wroot = vim.fn.fnamemodify(vim.fn.expand(w.root), ':p')
     if file:sub(1, #wroot) == wroot then
       root, ext = wroot, w.ext or ext
@@ -340,7 +341,7 @@ function M.search(args)
     end
   end
   if root == '' then
-    local first = config.wiki_list()[1]
+    local first = wikis[1]
     if first then
       root = vim.fn.fnamemodify(vim.fn.expand(first.root), ':p')
       ext = first.ext or ext
@@ -818,9 +819,7 @@ end
 -- *before* placing the cursor, all in a single `vim.schedule` tick.
 -- The algorithm matches the LSP server's implementation in nuwiki-rs.
 
-local function is_table_row(line)
-  return line ~= nil and line:match('^%s*|.*|%s*$') ~= nil
-end
+local is_table_row = require('nuwiki.util').is_table_row
 
 local function table_cell_starts(line)
   -- Returns 1-based byte positions of each `|` separator. Cell N spans

lua/nuwiki/folding.lua

@@ -9,16 +9,7 @@
 local M = {}
 
 --- Heading level from one line of source. Returns 0 for non-headings.
-local function heading_level(line)
-  local lead = line:match('^%s*(=+)%s')
-  if not lead then return 0 end
-  local lvl = #lead
-  if lvl > 6 then return 0 end
-  -- Require a matching trailing run of `=`s.
-  local trail = line:match('%s(=+)%s*$')
-  if not trail or #trail ~= lvl then return 0 end
-  return lvl
-end
+local heading_level = require('nuwiki.util').heading_level
 
 --- `foldexpr` body. Returns a fold-marker string per `:help fold-expr`.
 function M.expr()

lua/nuwiki/keymaps.lua

@@ -29,13 +29,7 @@ end
 -- vimwiki's `vimwiki#base#goto_*_header` family does, just simpler:
 -- match `^\s*=` runs as heading lines.
 
-local function heading_level(line)
-  local lead = line and line:match('^%s*(=+)%s')
-  if not lead then return 0 end
-  local trail = line:match('%s(=+)%s*$')
-  if not trail or #trail ~= #lead then return 0 end
-  return #lead
-end
+local heading_level = require('nuwiki.util').heading_level
 
 local function jump_heading(direction, predicate)
   local total = vim.api.nvim_buf_line_count(0)

lua/nuwiki/textobjects.lua

@@ -15,13 +15,7 @@ local M = {}
 
 -- ===== Heading helpers =====
 
-local function heading_level(line)
-  local lead = line and line:match('^%s*(=+)%s')
-  if not lead then return 0 end
-  local trail = line:match('%s(=+)%s*$')
-  if not trail or #trail ~= #lead then return 0 end
-  return #lead
-end
+local heading_level = require('nuwiki.util').heading_level
 
 --- Find the start/end of the heading block at `lnum`.
 --- `with_subtree` controls whether we descend into sub-headings:
@@ -123,9 +117,7 @@ end
 
 -- ===== Table cell / column =====
 
-local function is_table_row(line)
-  return line:match('^%s*|.*|%s*$') ~= nil
-end
+local is_table_row = require('nuwiki.util').is_table_row
 
 --- Compute the byte ranges of cells on a `|`-delimited row.
 --- Returns a list of `{start_byte, end_byte}` 1-based inclusive of the

lua/nuwiki/util.lua

@@ -0,0 +1,31 @@
+-- lua/nuwiki/util.lua — small pure-text helpers shared across the client
+-- layers (keymaps, folding, textobjects, commands). Dependency-free so any
+-- module can require it without load-order concerns.
+
+local M = {}
+
+-- Heading level of `line` (1-6), or 0 when it isn't a heading. Mirrors the
+-- server lexer: balanced leading/trailing runs of `=` around non-empty text,
+-- capped at level 6 (a 7+ `=` run is not a heading). `nil`-safe.
+function M.heading_level(line)
+  local lead = line and line:match('^%s*(=+)%s')
+  if not lead then
+    return 0
+  end
+  local lvl = #lead
+  if lvl > 6 then
+    return 0
+  end
+  local trail = line:match('%s(=+)%s*$')
+  if not trail or #trail ~= lvl then
+    return 0
+  end
+  return lvl
+end
+
+-- True when `line` looks like a table row (`| … |`). `nil`-safe.
+function M.is_table_row(line)
+  return line ~= nil and line:match('^%s*|.*|%s*$') ~= nil
+end
+
+return M