fix: the "Add to library" block in a question preview was three faults at once

It said library and meant collection. Its dropdown was always empty,
because the only page that renders this preview passes no collections —
so it read "Choose collection…" with nothing under it. And the "New
library…" input called setCollections, which does not exist in that
component: typing a name and pressing Enter created the collection,
added the question to it, and then threw a ReferenceError. Twelve lines,
none of which worked as written.

Removed rather than repaired. This preview is a moderator's editing
surface; putting a question aside is a learner's act and already lives
in the session and reading flows, where the collections are actually
loaded.

While there, the same word elsewhere: the Collections page called its
own contents "the question libraries you keep", which is the mislabel
the user spotted, on the page named after the other word. A library here
is the article library or an image library; a collection is what a
learner puts aside.

Found by the ped-ai session; the ReferenceError is mine to have missed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TqXevQJhxFrM7jJg82cgZN

frontend/src/components/FolderPicker.jsx

@@ -5,7 +5,7 @@ import './FolderPicker.css'
 /**
  * File the selected questions into a folder, for assignment.
  *
- * A folder is not a library. A library is what a learner puts aside for
+ * A folder is not a collection. A collection is what a learner puts aside for
  * themselves and the API says so on every row; a folder is a list an educator
  * assembles so that a grant can point at it, which is the one shape the access
  * tree — exam, discipline, category — cannot express.

frontend/src/components/QuestionPreview.jsx

@@ -18,7 +18,15 @@ const TeachChat = lazyPage(() => import('./TeachChat'))
  * Favourites and personal folders are optional and off by default — those
  * belong to studying a question, not to looking through the bank.
  */
-export default function QuestionPreview({ question, onClose, isFavorited, onToggleFavorite, collections = [] }) {
+/* No "Add to library" here any more. It was three faults in one twelve-line
+   block: it said library and meant collection; its dropdown was always empty,
+   because the only page that renders this preview passes no collections; and
+   the "New library…" input called setCollections, which does not exist in this
+   component — so typing a name and pressing Enter created the collection,
+   added the question, and then threw a ReferenceError. Putting a question
+   aside belongs to the reading and session flows, where the collections are
+   actually loaded; this is a moderator's editing preview. */
+export default function QuestionPreview({ question, onClose, isFavorited, onToggleFavorite }) {
   return (
     <>
       <div style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.55)', zIndex: 1000, display: 'flex', alignItems: 'center', justifyContent: 'center', padding: 16 }}
@@ -101,27 +109,6 @@ export default function QuestionPreview({ question, onClose, isFavorited, onTogg
             </div>
           )}
           <QuestionReadingLinks questionId={question.id} />
-          <div style={{ marginTop: 12, borderTop: '1px solid var(--border)', paddingTop: 10, fontSize: '0.85rem' }}>
-            <strong>Add to library</strong>
-            <div style={{ display: 'flex', gap: 8, marginTop: 6, flexWrap: 'wrap' }}>
-              <select defaultValue="" onChange={async e => {
-                if (!e.target.value) return
-                await api.put(`/collections/${e.target.value}/questions/${question.id}`)
-                e.target.value = ''
-              }} aria-label="Add to collection">
-                <option value="">Choose collection…</option>
-                {collections.map(c => <option key={c.id} value={c.id}>{c.title}</option>)}
-              </select>
-              <input placeholder="New library…" aria-label="New library name" onKeyDown={async e => {
-                if (e.key === 'Enter' && e.target.value.trim()) {
-                  const res = await api.post('/collections/', { title: e.target.value.trim() })
-                  await api.put(`/collections/${res.data.id}/questions/${question.id}`)
-                  setCollections(prev => [...prev, res.data])
-                  e.target.value = ''
-                }
-              }} style={{ padding: '4px 10px', border: '1px solid var(--border)', borderRadius: 6, fontSize: '0.8rem' }} />
-            </div>
-          </div>
           <div style={{ marginTop: 14, display: 'flex', gap: 8 }}>
             <button className="btn btn-secondary btn-sm" onClick={onClose}>Close</button>
           </div>

frontend/src/pages/CollectionsPage.jsx

@@ -42,11 +42,11 @@ function Shelf({ rows, onDrop }) {
 }
 
 /**
- * Everything a learner has put aside: the star, and the libraries they made.
+ * Everything a learner has put aside: the star, and the collections they made.
  *
  * Sorted by when each was last used rather than when it was made, because the
  * order things were created in is nobody's mental model of their own shelf.
- * A library nobody has opened falls back to its age — it is newer to the
+ * A collection nobody has opened falls back to its age — it is newer to the
  * learner than it is to the database.
  */
 export default function CollectionsPage() {
@@ -179,7 +179,7 @@ export default function CollectionsPage() {
       <div className="col-head">
         <h1>Collections</h1>
         <p>
-          The question libraries you keep. Favourites are not here — they are
+          The question collections you keep. Favourites are not here — they are
           marked while you sit a session, and sat again from the session
           builder, filtered by system or discipline like anything else.
         </p>