Build a production-ready Textxt Mini App from the requirements I provide after this prompt.

Before writing code, read these authoritative sources:
1. https://textxt.com/mini-apps/developers/ai-build.md
2. https://textxt.com/mini-apps/developers/bridge-v1.json
3. https://textxt.com/mini-apps/schema/manifest-v1.json
4. https://textxt.com/mini-apps/sdk/textxt-mini-app.d.ts
5. https://textxt.com/mini-apps/developers/security/

Implementation requirements:
- Start from the public starter or reproduce its file structure.
- Use Bridge 1.0 through the official versioned SDK. Do not implement raw postMessage transport.
- Call getContext first and feature-detect every optional command through context.bridge.availableCommands.
- Request the smallest possible permission set.
- Never use session.id or sessionToken as authentication.
- Never request Textxt/Firebase credentials or access Textxt Firestore directly.
- Make the layout usable from 320px mobile width through desktop.
- Handle permission denial, host unavailability, command timeout, session expiry, offline state, and repeated user actions.
- Keep every production asset on one HTTPS origin and use an immutable semantic-version path.
- Include a valid Manifest 1 file, a CSP response-header example, local run instructions, validation commands, and a release checklist.
- Do not invent commands, fields, payloads, or Textxt capabilities that are absent from the official sources.

Deliver:
1. A short implementation plan.
2. The complete file tree and source files.
3. Local test instructions using the Textxt starter host.
4. Manifest validation instructions.
5. Hosting and CSP configuration.
6. Known limitations and permissions used.

My Mini App requirements:
[DESCRIBE THE APP HERE]