feat(studio): force advanced reflection during browser-test sessions (v0.7.2)

When at least one browser_test session is connected, every chat
message in Studio now auto-enables advanced reflection regardless of
the user toggle. The intent: during AI-driven UI testing, having a
second model produce a preliminary [RAPPORT PRÉALABLE] materially
improves which clicks the active model decides to perform and the
quality of the final ✓/✗ report.

- handlers_chat: derive wantReflection from body.AdvancedReflection
  OR (browserTestStore has any active session). The user toggle still
  works for normal conversations; tests just override it.
- Silent fallback when no inactive provider is configured (no error,
  no behaviour change for single-provider setups).
- Tests.jsx: add a hint explaining the auto-on behaviour so the user
  understands why the Studio toggle appears bypassed.
- Version 0.7.1 → 0.7.2 + CHANGELOG entry.

web/src/components/Tests.jsx

@@ -148,6 +148,9 @@ lesquels déclenchent une erreur console.`}
           <p style={{ margin: '8px 0 0', opacity: 0.75, fontSize: '0.85em' }}>
             L'IA dispose de l'outil <code>browser_test</code> avec les actions <code>list_clickables</code>, <code>click</code>, <code>console</code>, <code>eval</code>, <code>type</code>, <code>current_url</code>, <code>wait</code>, <code>summary</code>.
           </p>
+          <p style={{ margin: '8px 0 0', padding: 8, fontSize: '0.85em', background: 'var(--accent-bg, rgba(108,92,231,0.1))', border: '1px solid var(--accent, #6c5ce7)', borderRadius: 4 }}>
+            <strong>Réflexion avancée auto :</strong> tant qu'au moins une session de test est connectée, chaque message dans Studio utilise automatiquement la réflexion avancée — un second modèle (s'il est configuré) produit un rapport d'analyse préalable injecté dans le prompt actif. Le toggle Studio est ignoré pendant la session.
+          </p>
         </div>
       </section>