finish the carousel rename in the panels

Two of these were live: PageBuilderPanel still compared kind === 'gallery' in
two places, so a carousel block's editor and its Choose button were both dead
branches. The type checker could not see them — both compare against string.

The rest is copy somebody reads: "Change gallery", "Name a new gallery",
"Reading the gallery", "Add to this gallery", Home's Gallery heading, and the
"Create Gallery" file action, now "Carousel from folder".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/sections/PageBuilderPanel.tsx

@@ -162,7 +162,7 @@ export const PageBuilderPanel = () => {
   const [choosing, setChoosing] = useState<{ sectionId: number; column: number } | null>(null);
   /** The component being written, and where a new one would go. Null when the dialog is shut. */
   /*
-    Which gallery a block shows, while it is being chosen.
+    Which carousel a block shows, while it is being chosen.
 
     The same shape as `picking` and for the same reason: choosing a set is one act with one outcome, so
     there is nothing to draft and nothing to cancel out of afterwards. `carouselId` rides along so
@@ -274,7 +274,7 @@ export const PageBuilderPanel = () => {
 
     The effect below cannot do that job: bumping `rendered` runs it immediately, while `frameDoc` still
     points at the outgoing document — so it scrolled the page that was about to be replaced, and the
-    new one arrived at the top. Every write from the editor did that: reorder a gallery, lose your
+    new one arrived at the top. Every write from the editor did that: reorder a carousel, lose your
     place.
   */
   const partRef = useRef<string | null>(part);
@@ -474,7 +474,7 @@ export const PageBuilderPanel = () => {
     with one outcome, so there is nothing to draft and nothing to cancel out of afterwards.
 
     Photograph or video is not asked. The file already knows, and the site reads it off the extension
-    the way a gallery item always has — a kind stored here would be a second answer able to disagree.
+    the way a carousel item always has — a kind stored here would be a second answer able to disagree.
   */
   const saveVideo = async (url: string) => {
     if (!page || !picking) return;
@@ -494,7 +494,7 @@ export const PageBuilderPanel = () => {
   };
 
   /*
-    A gallery block is a REFERENCE, saved as soon as the set is chosen — see CarouselPicker.
+    A carousel block is a REFERENCE, saved as soon as the set is chosen — see CarouselPicker.
 
     Identical in shape to saveVideo because it is the same interaction: pick one thing, store one
     value. The two are left as two functions rather than one generic saver, because what they store
@@ -589,7 +589,7 @@ export const PageBuilderPanel = () => {
       return;
     }
 
-    if (component.kind === 'gallery') {
+    if (component.kind === 'carousel') {
       const held = owner.components.find((one) => one.id === component.id)?.content?.carouselId;
       setChoosingCarousel({
         id: component.id,
@@ -793,7 +793,7 @@ export const PageBuilderPanel = () => {
           */}
           {block.kind === 'partners' && <PartnersEditor onChanged={() => setRendered((n) => n + 1)} />}
 
-          {block.kind === 'gallery' && (
+          {block.kind === 'carousel' && (
             <div className="flex flex-col gap-3">
               <Button
                 size="sm"
@@ -801,13 +801,13 @@ export const PageBuilderPanel = () => {
                 className="h-8 self-start text-xs"
                 onClick={() => handlersRef.current.editComponent(block)}
               >
-                Choose gallery…
+                Choose carousel…
               </Button>
 
               {/*
-                The gallery's own contents, here rather than a link to the Carousels section.
+                The carousel's own contents, here rather than a link to the Carousels section.
 
-                A gallery block on a page IS a gallery, and being sent elsewhere to reorder it means
+                A carousel block on a page IS a carousel, and being sent elsewhere to reorder it means
                 losing the page you were arranging it for. `onChanged` reloads the frame, because the
                 page draws this set and has just been given a different one.
               */}