release: publish installable web demo path

Goal

Make AI Language Partner easier for non-contributors and external directory maintainers to try. This is the follow-up to the Awesome Japanese maintainer feedback that readers need a clearer way to use the app before it fits that directory.

Acceptance

• Document the current one-origin web demo path from docs/community/INSTALLABLE_DEMO_RELEASE_PLAN.md.
• Verify apps/mobile can run npm run verify.
• Verify apps/api can run its test suite in mock mode.
• Verify npx expo export --platform web succeeds, or document the exact blocker.
• Verify apps/api/scripts/serve_demo.py serves the exported web app and /health from one origin, or document the exact blocker.
• Add release/demo notes that clearly label mock providers, fixture-backed content, and missing local STT/TTS behavior.
• Do not commit generated screenshots, .wav, .zip, .npy, .sqlite, local engines, secrets, or private notes.

Why this matters

This does not count as Claude for OSS evidence by itself. It improves the project maturity and user-facing install path, which should make external contributor discovery and future directory submissions more credible.

Related doc: docs/community/INSTALLABLE_DEMO_RELEASE_PLAN.md