Review desk: announced pages (portal_events)

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

README.md

@@ -180,8 +180,9 @@ Question            id (derived from the file's path - see routing
                     requires_chain (question ref the visitor's ?chain=
                     lineage must end at), followup (nav-hidden until
                     the visitor carries a chain; inferred from the
-                    tree when unset), responsible {name, contact},
-                    alternatives[]
+                    tree when unset), event {starts, duration, place}
+                    (announced page - see below), responsible
+                    {name, contact}, alternatives[]
   Alternative       name, description, action, disabled (announced,
                     not yet takeable), consequence[label],
                     encouragements[], images[] (1 = banner, 2+ = card deck),
@@ -236,6 +237,28 @@ review resource's transitions — fireable by whoever holds one specific
 record's `?chain=` link plus its matching email (the unsubscribe
 pattern).
 
+**Announced pages.** A question carrying an `event:` block
+
+```yaml
+event:
+  starts: 2026-09-12T18:00:00+02:00   # RFC 3339, with offset
+  duration: 3h                        # m / h / d, e.g. "1d 6h"
+  place: Galleri X, Oslo              # optional, shown verbatim
+```
+
+is announced in the header of every page (name, when, "in 3 days")
+while its window is open, instead of listed in the footer nav. The
+page itself is an ordinary question - RSVP, directions, whatever its
+alternatives say. When the window closes the page turns into a
+followup (only visitors carrying an answer chain still see it) and
+portal moves the page's record in the runtime-owned `portal_events`
+bucket from `announced` to `awaiting_summary`, publishing that on
+`portal.answers.submitted` like any decision (alternative "Summary
+due") - the "post what happened" task. `/review`'s "Announced pages"
+desk reads that bucket; **Posted what happened** closes the task.
+Lint warns when pages carry `event:` but nothing reads
+`portal_events`.
+
 **Attended buckets** (lint-enforced): every `record_as` bucket must be
 read by some `kv` resource in this repo (a desk or listing) — or its
 `aggregates.yaml` entry must carry `attended_by: <who/what consumes