refactor(man.lua): various changes

- Replace all uses of vim.regex with simpler Lua patterns.
- Replace all uses of vim.fn.substitute with string.gsub.
- Rework error handling so expected errors are passed back via a return.
  - These get routed up an passed to `vim.notify()`
  - Any other errors will cause a stack trace.
- Reworked the module initialization of `localfile_arg`
- Updated all type annotations.
- Refactored CLI completion by introduction a parse_cmdline()
  function.
- Simplified `show_toc()`
- Refactor highlighting
- Inline some functions
- Fix completion on MacOS 13 and earlier.
  - Prefer `manpath -q` over `man -w`
- Make completion more efficient by avoiding vim.fn.sort and vim.fn.uniq
  - Reimplement using a single loop

runtime/plugin/man.lua

@@ -8,9 +8,9 @@ vim.api.nvim_create_user_command('Man', function(params)
   if params.bang then
     man.init_pager()
   else
-    local ok, err = pcall(man.open_page, params.count, params.smods, params.fargs)
-    if not ok then
-      vim.notify(man.errormsg or err, vim.log.levels.ERROR)
+    local err = man.open_page(params.count, params.smods, params.fargs)
+    if err then
+      vim.notify('man.lua: ' .. err, vim.log.levels.ERROR)
     end
   end
 end, {
@@ -31,6 +31,9 @@ vim.api.nvim_create_autocmd('BufReadCmd', {
   pattern = 'man://*',
   nested = true,
   callback = function(params)
-    require('man').read_page(vim.fn.matchstr(params.match, 'man://\\zs.*'))
+    local err = require('man').read_page(assert(params.match:match('man://(.*)')))
+    if err then
+      vim.notify('man.lua: ' .. err, vim.log.levels.ERROR)
+    end
   end,
 })