build: enable more EmmyLua checks

- call-non-callable
- missing-fields
- redefined-label
- redefined-local
- undefined-field
- unreachable-code

Promote redefined-local and unreachable-code to warnings.

Fix DOS line-ending handling for multiline semantic tokens, and support
intersection types in the help parser.

AI-assisted

runtime/lua/vim/_watch.lua

@@ -245,9 +245,9 @@ function M.watchdirs(path, opts, callback)
   for name, type in
     vim.fs.dir(path, {
       depth = max_depth,
-      skip = function(name)
+      skip = function(dir)
         return not opts.exclude_pattern
-          or opts.exclude_pattern:match(vim.fs.joinpath(path, name)) == nil
+          or opts.exclude_pattern:match(vim.fs.joinpath(path, dir)) == nil
       end,
     })
   do