test(post-form): retarget suite to redesigned /post + add UX coverage (U7)

- test-form-config.sh: assert parent is NOT hardcoded (injected server-side),
  active_trip set in site.yaml, and the new fields incl. custom 'photos' type.
- helpers.js: resolve active trip from site.active_trip (parent coupling gone);
  fillEditor() drives EasyMDE via window.postFormEditor; waitForPhotoUpload()
  waits on the new picker.
- post.spec / validation.spec: content via the editor, filepond selectors ->
  the photo picker, P8 checks editor value, V3/V4 exercise the picker cap +
  fail-closed non-image.
- post-form-ux.spec.js (new): AE3 disclosure, AE1 HEIC->JPEG, AE4 corrupt-HEIC
  fail-closed, R18 weather gating, R20 draft restore.
- fixtures: real + corrupt .heic.
- test-post.sh: resolve dailies dir from active_trip.

Refs AE1-AE4, R18, R20, U7.

scripts/test-post.sh

@@ -7,7 +7,11 @@ set -euo pipefail
 BASE_URL="${GRAV_BASE_URL:-http://localhost:8081}"
 USER="${GRAV_TEST_USER:-}"
 PASS="${GRAV_TEST_PASS:-}"
-TRACKER="user/pages/01.trips/japan-korea-2026/01.dailies"
+# Parent is injected server-side from site.active_trip (U1), so resolve the
+# dailies dir from site.yaml rather than hardcoding a trip slug.
+ACTIVE_TRIP=$(grep -E '^active_trip:' user/config/site.yaml | head -1 | sed -E "s/^active_trip:[[:space:]]*['\"]?//; s/['\"]?[[:space:]]*\$//")
+TRIP_SLUG=$(basename "${ACTIVE_TRIP%/}")
+TRACKER="user/pages/01.trips/${TRIP_SLUG:-italy-2026-demo}/01.dailies"
 COOKIE_JAR="$(mktemp /tmp/grav-test-cookies.XXXXXX)"
 PASS_COUNT=0
 FAIL_COUNT=0