wn-input/wn-select/wn-button aren't form-associated custom elements —
their real <input>/<select>/<button> live inside shadow DOM, invisible
to an ancestor <form>. Clicking Sign In (or any wn-button[type=submit])
silently did nothing, and even a submitted form would have carried none
of the field values. Bridges both gaps generically in base.html without
touching the vendored library: mirrors each shadow-DOM control's live
value into a hidden native input on submit, and explicitly calls
form.requestSubmit() on wn-button[type=submit] clicks.
Reported by the user clicking Sign In in the running local instance —
missed by test_control_plane_app.py because TestClient POSTs directly
and never exercises real button clicks or shadow DOM.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>