Improve Ava voice, continuity, and message clarity

[codeyogi911]

What changed

• stream Ava's TTS response audio and report first-audio pipeline metrics
• suppress microphone capture while assistant audio is playing to prevent self-interruption loops
• preserve and hydrate the same support conversation across Shopify customer sign-in
• refuse cart, checkout, payment, and order-placement claims when no write capability exists
• render outgoing customer messages with an accessible blue treatment

Why

Customers were waiting too long for audible responses, Ava could hear and interrupt herself, the browser discarded visible history after hosted sign-in, and purchase requests could receive an unverified success claim. Outgoing messages also lacked a strong, consistent sender distinction.

Impact

Voice replies begin playing progressively, the microphone is protected during assistant playback, authenticated returns keep the existing conversation visible, and Ava states truthfully that nothing was ordered or charged. Customer messages now use a blue-on-pale-blue treatment with measured WCAG AA contrast.

Validation

• npm run check
• hosted Workers AI voice eval, including immediate and post-login order-placement cases
• focused Shopify sign-in/history/order Worker suite: 67 tests
• focused mobile Playwright sign-in-return test
• focused mobile Playwright outgoing-message contrast test: 5.51:1