fix(frontend): show the server's reason for each excluded RI on the exchange page

frontend/src/__tests__/riexchange.test.ts

@@ -1594,12 +1594,40 @@ describe('excluded RIs notice', () => {
     await loadReshapeRecommendations();
 
     const notice = document.getElementById('ri-exchange-recommendations-excluded');
-    expect(notice?.textContent).toContain('2 convertible RIs were left out because AWS returned no term length');
+    expect(notice?.textContent).toContain('2 convertible RIs were left out because no term');
     expect(notice?.textContent).toContain('ri-0');
     expect(notice?.textContent).toContain('<img src=x onerror=alert(1)>');
     expect(notice?.querySelector('img')).toBeNull();
   });
 
+  it('shows each excluded RI\'s server reason, grouped by reason', () => {
+    renderExcludedRIsNotice([
+      { ri_id: 'ri-dur', reason: 'non-positive duration' },
+      { ri_id: 'ri-price', reason: 'no pricing available' },
+    ]);
+    const text = document.getElementById('ri-exchange-recommendations-excluded')?.textContent ?? '';
+    expect(text).toContain('1 convertible RI was left out because non-positive duration: ri-dur');
+    expect(text).toContain('1 convertible RI was left out because no pricing available: ri-price');
+    expect(text).not.toContain('no term length');
+  });
+
+  it('falls back to the term-length text when reason is empty or missing', () => {
+    renderExcludedRIsNotice([
+      { ri_id: 'ri-a', reason: '' },
+      { ri_id: 'ri-b' } as unknown as { ri_id: string; reason: string },
+    ]);
+    expect(document.getElementById('ri-exchange-recommendations-excluded')?.textContent).toContain(
+      '2 convertible RIs were left out because AWS returned no term length: ri-a, ri-b',
+    );
+  });
+
+  it('renders a reason containing HTML special characters as text', () => {
+    renderExcludedRIsNotice([{ ri_id: 'ri-x', reason: '<b>bad</b> & "quoted"' }]);
+    const notice = document.getElementById('ri-exchange-recommendations-excluded');
+    expect(notice?.textContent).toContain('<b>bad</b> & "quoted"');
+    expect(notice?.querySelector('b')).toBeNull();
+  });
+
   it('shows no notice when excluded_ris is empty or absent, and clears a stale one', () => {
     renderExcludedRIsNotice([{ ri_id: 'ri-0', reason: 'x' }]);
     expect(document.getElementById('ri-exchange-recommendations-excluded')?.textContent).toContain('1 convertible RI was left out');

frontend/src/riexchange.ts

@@ -588,9 +588,18 @@ export function renderExcludedRIsNotice(excluded: ExcludedRI[] | undefined): voi
     notice.className = '';
     return;
   }
-  const n = excluded.length;
+  const byReason = new Map<string, string[]>();
+  for (const e of excluded) {
+    const reason = e.reason || 'AWS returned no term length';
+    const ids = byReason.get(reason);
+    if (ids) ids.push(e.ri_id);
+    else byReason.set(reason, [e.ri_id]);
+  }
   notice.className = 'freshness-banner warning';
-  notice.textContent = `${n} convertible RI${n === 1 ? ' was' : 's were'} left out because AWS returned no term length: ${excluded.map((e) => e.ri_id).join(', ')}`;
+  // textContent keeps server-provided reasons and ids inert.
+  notice.textContent = [...byReason]
+    .map(([reason, ids]) => `${ids.length} convertible RI${ids.length === 1 ? ' was' : 's were'} left out because ${reason}: ${ids.join(', ')}`)
+    .join('; ');
 }
 
 /**