test(fixture): add no-photos-demo trip for AE4 coverage

A minimal demo trip with no cover_image and a single published journal entry
that has no images — the fixture the trip-page banner AE4 assertion needs
(macro fallback loop finds an entry but no image -> null cover -> no banner
strip). Lives under docs/demo/trips/ like italy-2026-demo, so it is loaded into
the pages tree only for tests and never reaches live content.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RDS6t8wcpbwKvvrxykVQ5K

docs/demo/trips/no-photos-demo/trip.md

@@ -0,0 +1,14 @@
+---
+title: 'Notes from the Road 2027'
+template: trip
+date: '2027-01-10'
+date_start: '2027-01-10'
+date_end: '2027-01-14'
+cover_image: ''
+tagline: 'A text-only journal, written before the photos catch up'
+---
+
+A short winter trip recorded in words only — no camera this time, just a
+notebook and whatever the road turned up. The entries stand on their own until
+the film comes back from the lab, so this one is a deliberate test of how the
+trip page reads with nothing but text to show.