fix(desktop): simplify partial history notice

[Sun-GLiang]

Summary

Follow up on the partial-history review from #3880:

• present historical position as a quiet reading-column notice with a small text action to return to the latest messages
• keep the prompt rail focused on turn and request anchors by removing residency-specific hollow ticks
• preserve conversation message cards and composer behavior
• add a real Electron fixture and E2E coverage for the return-to-latest transition

Verification

• npm run build
• npm run lint — 2920 files checked
• npm run format:check — 1762 files checked
• npm --workspace @maka/ui run build && npm --workspace @maka/desktop run typecheck
• npm --workspace @maka/ui test — 264 passed
• npx playwright test --config e2e/playwright.config.ts e2e/partial-history-notice.spec.ts — 1 passed
• git diff --check upstream/main...HEAD

The repository-wide npm test is not green on this macOS host because of unrelated Runtime and CLI test isolation/path assumptions tracked in #4139. The affected UI and Desktop checks above pass locally.

UI evidence

Before — boxed status notice

After — quiet reading-position notice

The signed-in conversation, sidebar, message cards, and composer are intentionally unchanged; the comparison focuses on the top-of-thread reminder.

AI use

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: OpenAI Codex — implementation, test coverage, scope validation, and PR preparation.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No

[Astro-Han]

Thanks for following up on the partial-history presentation. This change removes the locally authored boxed surface rather than replacing it with another one: the notice is composed from Astryx HStack, Text, and Button primitives, while product CSS only applies the existing reading measure and spacing tokens. The prompt rail likewise removes its custom residency chrome and keeps the existing Astryx control surface.

The dedicated E2E fixture is justified here because it crosses the real bounded-history threshold and exercises the load-around, responsive presentation, and return-to-latest transition end to end. The Astryx surface inventory and current CI pass, and the visual direction has been manually confirmed. I found no P0–P2 issue.

Reviewed with OpenAI Codex as an AI-assisted review; I verified Astryx primitive and token usage, prompt-rail simplification, the bounded-history interaction path, focused tests, and current CI.

中文对照

谢谢你继续收敛部分历史记录的呈现方式。本次改动删除了局部自绘的盒状 surface，而不是换成另一套自定义实现：提示使用 Astryx 的 HStack、Text 和 Button 原语组合，产品 CSS 只应用已有的阅读列宽度与间距 token。Prompt rail 同样删除了自定义 residency 样式，继续使用既有的 Astryx 控件。

独立 E2E fixture 在这里是合理的，因为它真实跨过历史加载上限，并端到端验证 load-around、响应式呈现和返回最新消息的交互。Astryx surface inventory 与当前 CI 均通过，视觉方向也已经由维护者人工确认。没有发现 P0–P2 问题。

本次审查由 OpenAI Codex 辅助完成；我核对了 Astryx 原语与 token、prompt rail 收敛、有限历史交互路径、定向测试和当前 CI。