A card of one's own: one_per_person, prefilled, replaced on send; no double sends; refusals are shown

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GT37Z1Xtfd9pUuQtMTg6Yt

src/content/validate.rs

@@ -512,6 +512,13 @@ pub fn validate_questions(
     }
     for question in questions.values() {
         for alternative in &question.alternatives {
+            if alternative.one_per_person && alternative.record_as.is_none() {
+                anyhow::bail!(
+                    "question {:?} alternative {:?}: one_per_person keeps each person's own record, and there is no record_as to keep it in",
+                    question.id,
+                    alternative.name
+                );
+            }
             if let Some(bucket) = &alternative.record_as {
                 let attended = read_buckets.contains(bucket)
                     || aggregates