audit: comprehensive cleanup — delete 8 files, fix buffer bug, cut bloat

tests/helpers.lua

@@ -0,0 +1,9 @@
+local M = {}
+
+function M.assert_eq(a, b, msg)
+  if a ~= b then
+    error(string.format("FAIL: %s — expected %s, got %s", msg, vim.inspect(b), vim.inspect(a)))
+  end
+end
+
+return M