feat(demo): refresh cloud demo for latest EverOS

[Yangtze-Seventh]

Summary

Rebuilds the interactive EverOS demo on top of the latest main as a clean, single-commit change. This supersedes #306 without carrying its outdated commit history.

What changed

• Makes everos demo an interactive cloud-backed first-run experience.
• Visualizes the ingest, extract, index, and recall lifecycle with a unified particle sphere and continuous stage transitions.
• Uses the EverMind Cloud v2 memory API while keeping credentials server-side.
• Preserves recalled memory across demo rounds and prioritizes the current round when appropriate.
• Supports Chinese IME input and keeps plain/cinematic offline previews.
• Adds a Netlify relay with endpoint allowlisting, distributed rate limits, and a three-round daily quota.
• Refreshes the English and Chinese demo documentation and animated preview.

Developer impact

Developers can run everos demo locally and experience memory ingestion, extraction, indexing, and recall through a short interactive conversation without configuring the full EverOS stack first.

Validation

• make lint
• 2090 unit tests passed
• 182 integration tests passed (7 deselected)
• 9 Netlify relay tests passed
• Conventional Commit subject and PR title checks passed

Supersedes #306.

[Yangtze-Seventh]

readme.-github.webm