Announced pages: event windows, header announcements, summary tasks

A question may carry event: {starts, duration, place}. While the
window is open the page is announced in a strip at the top of every
header (name, when, 'in 3 days'), soonest first, and kept out of the
footer nav; when it closes the page becomes a followup - only a
visitor carrying an answer chain still sees it.

announce.rs keeps one record per event page in the runtime-owned
portal_events bucket (built-in state graph: announced ->
awaiting_summary -> summarized, content may override) and, on a
one-minute idempotent sweep, moves ended windows to awaiting_summary,
publishing the transition on portal.answers.submitted as 'Summary
due' - the post-what-happened task a review desk picks up. Lint
warns when event pages exist but nothing reads portal_events.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bin/question_lint.rs

@@ -52,8 +52,21 @@ async fn main() -> anyhow::Result<()> {
         eprintln!("FAIL: {e}");
         std::process::exit(1);
     }
+    let aggregates_map = content::with_builtin_aggregates(aggregates_map);
     match content::validate_questions(&questions, &aggregates_map) {
         Ok(()) => {
+            // The runtime's own event desk: a repo announcing pages
+            // (Question.event) should read portal_events somewhere, or
+            // "post what happened" tasks pile up unseen. Warn, don't
+            // fail - the runtime creates the records either way.
+            if questions.values().any(|q| q.event.is_some())
+                && !content::bucket_is_read(&questions, content::EVENTS_BUCKET)
+            {
+                eprintln!(
+                    "WARN: pages carry `event:` but no kv resource reads bucket {:?} - add a desk so summaries get posted",
+                    content::EVENTS_BUCKET
+                );
+            }
             println!(
                 "OK: {} question(s), {} aggregate(s) valid",
                 questions.len(),