fix: nil-guard in _invoke_context_menu + README English

- _invoke_context_menu now early-returns if locale_factory()
  returns nil mid-frame, symmetric with build_rows. Prevents the
  race where a workbench destroyed between render and right-click
  would propagate nil locale into ctx_inner and crash craft.
- README v0.2.0 sections (M.create + action-callback) translated
  from Denglisch to English for consistency with the rest of the
  file.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

init.lua

@@ -296,6 +296,7 @@ end
 
 function M._invoke_context_menu(widget, recipe_id, mx, my)
     local locale = widget._locale_factory()
+    if locale == nil then return end  -- symmetric with build_rows
     local sink_alias
     if type(locale) == "table" then
         sink_alias = locale.sink