truapi-host: show permission and confirmation prompts inside the product

[pgherveou]

Part of #517.

Context

Confirmations render in the terminal today, and truapi-host dev auto-approves every one of them. A product developer therefore never sees what a user sees, and code that mishandles a denied permission still looks correct locally. Auto-approval should be the shortcut, not the whole experience.

The CLI already serves the bridge the product loads, so it can also draw host-owned UI into the page, the way a mobile host draws its own sheet over a product.

Required behavior

• The bridge can render permission and confirmation prompts as an overlay in the product page, owned by the host and not by the product.
• Prompts sit close enough to the mobile hosts that a developer feels the same interruption, including denial.
• Manual approval is the default for those prompts; auto-approve stays opt-in for scripted runs.
• The terminal transcript still records every request, so --script and CI runs are unaffected.
• Products with no standing grant get the full prompt path, which is what makes this useful for developers outside the trusted set.

Related: docs/rfcs/0002-permission-model.md.