Degrade Stream by capability

[cauyxy]

Summary

• Split Stream into independent service, polling freshness, display-window, crop, and one-off action capabilities.
• Preserve semantic problems across Rust/Specta/API boundaries and localize recovery copy only at presentation time.
• Keep the live workflow stable across locale changes and distinguish stale status from authoritative stopped or failed state.
• Refresh current truth documentation with implementation-backed citations.

Testing

• npm run check
• npm run test:unit
• npm run test:rust
• npm run verify -- --source-only
• Browser Preview at 127.0.0.1:14207/stream in English and Chinese; no console warnings/errors or viewport overflow
• macOS npm run tauri dev startup smoke; real install/database detected and overlay returned HTTP 200
• Native dev window could not be attached for automated UI interaction; no state-changing Stream action was executed

Closes #26

Release Notes:

• 直播页现在会按服务、轮询、展示窗口和叠加层配置分别降级，并在切换语言时保持当前直播会话。

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Count slow poll failures before keeping status fresh

When getStatus() failures take longer than the 2s polling interval, each later interval increments latestPollRequest before the earlier request rejects, so this guard discards every failed response as outdated. With no newer successful status, consecutivePollFailures never reaches the threshold and the snapshot stays fresh, leaving running-only controls enabled against an actually stale service state; the failure path should ignore only failures older than a newer success, not older than any newer request.

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