fix(dir): do not swallow errors raised after the list callback

Problem:  An error raised after the list handler ran (e.g. while
          rendering) unwinds through the pcall around provider.list()
          and is routed back into the now no-op handler: silently
          discarded.
Solution: Re-raise the error when the handler has already run.

runtime/lua/nvim/dir.lua

@@ -268,6 +268,10 @@ function load(buf, name, provider, restore_view, setup, select)
 
   local ok, call_err = pcall(provider.list, buf, name, on_list) ---@type boolean, any
   if not ok then
+    if done then
+      -- The handler already ran and would ignore this error: propagate it.
+      error(call_err, 0)
+    end
     -- Route provider exceptions through the list handler so failures share one cleanup path.
     on_list(tostring(call_err), nil)
   end