The farewell overlay already attempted ``window.top.close()`` after a
Close click — but browsers only honour that for tabs that JS opened
(Chrome --app windows qualify; a regular browser tab does not). For
users whose Chrome wasn't auto-detected and who fall back to
``webbrowser.open``, the overlay stays put and they had no in-page
way to close.
Add to the overlay HTML:
- A "Close this window" button (uses the user-gesture path, which has
slightly looser browser rules than auto-close).
- A hidden hint paragraph that reveals itself 250 ms after the
button is clicked IF the window is still here, telling the user to
press Ctrl+W (⌘W on Mac).
Wired through the existing _farewell_script template + ``_js_html_safe``
escaping so neither label can break out of the JS string literal.
New i18n keys (en + es): ``quit.close_window_button`` and
``quit.close_hint``.
The existing auto-close attempt remains — Chrome --app users still get
their window closed without touching the button.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>