renderQuestions() was calling root.replaceChildren() on every
question_added / question_resolved SSE event, wiping all <li>
elements including any textarea the operator was typing into.
Add questionRowCache (Map<id, {el, fingerprint}>):
- questionRowFingerprint encodes the static fields that determine
the <li> DOM structure (asker, target, asked_at, deadline_at,
question text, options, multi)
- buildQuestionLi extracts the <li>-building code so it can be
called only when the fingerprint changes
- renderQuestions reuses cached <li> nodes for unchanged questions
and evicts entries for resolved/cancelled questions
Effect: when a new question arrives while the operator is typing a
reply, the existing <li> is reused — the textarea value, radio
selection, and checkbox state are all preserved.
The history <details> open state is also saved before and restored
after the replaceChildren call, so the answered-history panel does
not collapse when a live question event fires.
b15d7a4b5d