add image picker to page editor and fix thumbnail layout

Wire up image field in block settings with a modal picker that
browses the media library. Fix picker thumbnails collapsing to
14px by replacing overflow:hidden with overflow:clip on grid
items (hidden sets min-height:0 in grid context). Polish media
library mobile sheet with scrim overlay and tighter spacing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/css/admin/components.css

@@ -1662,6 +1662,139 @@
   font-size: 0.8125rem;
 }
 
+.image-field-actions {
+  display: flex;
+  gap: 0.375rem;
+}
+
+.image-field-remove-btn {
+  color: var(--t-accent);
+}
+
+.image-field-choose-btn {
+  width: 100%;
+  justify-content: center;
+}
+
+/* ── Image picker modal ─────────────────────────────────────────── */
+
+.image-picker-overlay {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.3);
+  z-index: 50;
+  display: flex;
+  align-items: flex-end;
+  justify-content: center;
+
+  @media (min-width: 40em) {
+    align-items: center;
+  }
+}
+
+.image-picker {
+  background: var(--t-surface-base);
+  border-radius: 0.75rem 0.75rem 0 0;
+  width: 100%;
+  max-height: 80vh;
+  overflow-y: auto;
+  padding: 1rem;
+  display: flex;
+  flex-direction: column;
+
+  @media (min-width: 40em) {
+    border-radius: 0.75rem;
+    max-width: 32rem;
+  }
+}
+
+.image-picker-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 0.75rem;
+
+  & h3 {
+    font-size: 1rem;
+    font-weight: 600;
+  }
+}
+
+.image-picker-search {
+  width: 100%;
+  margin-bottom: 0.75rem;
+}
+
+.image-picker-grid {
+  display: grid;
+  grid-template-columns: repeat(2, 1fr);
+  gap: 0.5rem;
+  overflow-y: auto;
+
+  @media (min-width: 40em) {
+    grid-template-columns: repeat(3, 1fr);
+  }
+}
+
+.image-picker-item {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 0.375rem;
+  padding: 0.375rem;
+  border: 1px solid var(--t-border-default);
+  border-radius: 0.375rem;
+  background: none;
+  cursor: pointer;
+  text-align: center;
+  color: inherit;
+  transition: background 100ms;
+  overflow: clip;
+  min-width: 0;
+
+  @media (hover: hover) {
+    &:hover {
+      background: var(--t-surface-sunken);
+    }
+  }
+}
+
+.image-picker-item-thumb,
+.image-picker-item-svg {
+  width: 100%;
+  aspect-ratio: 1;
+  border-radius: 0.25rem;
+  background: var(--t-surface-sunken);
+}
+
+.image-picker-item-thumb {
+  object-fit: cover;
+}
+
+.image-picker-item-svg {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  color: var(--t-text-primary);
+  opacity: 0.5;
+}
+
+.image-picker-item-name {
+  font-size: 0.6875rem;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  max-width: 100%;
+}
+
+.image-picker-empty {
+  grid-column: 1 / -1;
+  text-align: center;
+  padding: 1.5rem;
+  color: color-mix(in oklch, var(--t-text-primary) 50%, transparent);
+  font-size: 0.8125rem;
+}
+
 /* ═══════════════════════════════════════════════════════════════════
    Media library
    ═══════════════════════════════════════════════════════════════════ */
@@ -1913,13 +2046,27 @@
   padding-top: 0.75rem;
 }
 
+.media-detail-scrim {
+  display: none;
+}
+
 @media (max-width: 47.99em) {
   .media-grid {
     grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
   }
 
+  .media-detail-scrim {
+    display: block;
+    position: fixed;
+    inset: 0;
+    background: rgba(0, 0, 0, 0.5);
+    z-index: 39;
+    animation: media-scrim-fade 0.2s ease-out;
+  }
+
   .media-detail {
     position: fixed;
+    top: auto;
     bottom: 0;
     left: 0;
     right: 0;
@@ -1927,9 +2074,32 @@
     min-width: unset;
     max-height: 70vh;
     border-radius: 0.75rem 0.75rem 0 0;
-    box-shadow: 0 -4px 24px rgba(0, 0, 0, 0.15);
+    box-shadow: 0 -4px 24px rgba(0, 0, 0, 0.25);
     z-index: 40;
     animation: media-sheet-up 0.25s ease-out;
+    padding: 0.75rem 1rem;
+    gap: 0.5rem;
+  }
+
+  .media-detail-preview {
+    display: none;
+  }
+
+  .media-detail-meta {
+    font-size: 0.75rem;
+    gap: 0.125rem 0.5rem;
+  }
+
+  .media-detail-form {
+    gap: 0.25rem;
+  }
+
+  .media-detail-form .admin-fieldset {
+    margin-bottom: 0;
+  }
+
+  .media-detail-form .admin-label {
+    font-size: 0.75rem;
   }
 }
 
@@ -1938,4 +2108,9 @@
   to { transform: translateY(0); }
 }
 
+@keyframes media-scrim-fade {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
 } /* @layer admin */