fix: AI Mode opens on the starters, not on a paragraph about itself

The rules were explained before anybody had asked anything. What the assistant
will and will not do is visible in the answers themselves — each carries its
sources, or says it has none — and a page that explains itself up front is a
page nobody reads.

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

frontend/src/pages/AiModePage.jsx

@@ -443,11 +443,6 @@ export default function AiModePage() {
 
         {blank && (
           <div className="ai-hero-foot">
-            <p className="ai-tip">
-              Answers come from your own articles, questions and cards, and each one
-              carries the source it came from. If your library does not cover
-              something, it says so instead of filling the gap.
-            </p>
             <ul className="ai-starters">
               {starters.map(starter => (
                 <li key={starter}>

frontend/src/pages/AiModePage.test.jsx

@@ -109,10 +109,15 @@ describe('AI Mode', () => {
     expect(await screen.findByRole('button', { name: 'What is jaundice?' })).toBeInTheDocument()
   })
 
-  it('is honest about what it will not do before you ask', async () => {
+  it('opens on the starters, with nothing to read first', async () => {
+    // The paragraph that used to explain the rules here is gone. What the
+    // assistant will and will not do is visible in the answers themselves —
+    // every one carries its sources, or says it has none — and a page that
+    // explains itself before anyone has asked anything is a page nobody reads.
     mockApi([])
     mount()
-    expect(await screen.findByText(/says so instead of filling the gap/)).toBeInTheDocument()
+    expect(await screen.findByRole('button', { name: /What does my library say about managing bronchiolitis/ })).toBeInTheDocument()
+    expect(document.querySelector('.ai-tip')).toBeNull()
   })
 
   it('deletes a thread and moves off it', async () => {