fix(form): render aria-busy as "true"/"false" on the create and save buttons #97

Follow-up to #88.

Problem #

The create and save buttons set aria-busy={submitting}. hono/jsx's DOM renderer writes a boolean true as an empty attribute, aria-busy="", which assistive technology reads as not busy. ARIA attributes take the strings "true" and "false". The rest of the codebase already passes them as strings (draggable="true", aria-expanded, aria-disabled="true" in AutomationToolbar.tsx).

Evidence #

• app/islands/AutomationForm.tsx:3592 (edit page) and app/islands/AutomationForm.tsx:3604 (New form): aria-busy={submitting}.

Expected #

While a submit is in flight, the button has aria-busy="true"; otherwise aria-busy="false" or no attribute.

Acceptance criteria #

• Both buttons render aria-busy="true" while submitting.
• A test in AutomationForm.test.tsx checks the rendered attribute value, not only its presence.