fix(images): cap the search at the listing API's 500 characters

A longer paste was sent as is, the API rejected it and the collection
showed "Images could not be loaded". The legacy search capped it.

tests/js/workspace-toolbar.test.js

@@ -138,6 +138,8 @@ test('toolbar emits concept markup and order', async () => {
         assert.equal(input.id, 'search');
         assert.equal(input.type, 'search');
         assert.equal(input.placeholder, 'Search prompts, tags, filenames…');
+        // The listing API rejects search text over 500 characters, as the legacy search capped it.
+        assert.equal(input.maxLength, 500);
         assert.equal(input.getAttribute('aria-label'), 'Search workspace');
         assert.equal(input.value, 'castle');
 

web/js/workspace/toolbar.mjs

@@ -68,6 +68,8 @@ export function mountToolbar(container, { scope, categories = [], sorts, value =
     search.id = 'search';
     search.type = 'search';
     search.placeholder = 'Search prompts, tags, filenames…';
+    // The listing API rejects longer search text (py/api/images.py _workspace_filters).
+    search.maxLength = 500;
     search.setAttribute('aria-label', 'Search workspace');
     label.append(createWorkspaceIcon('search'), search);