feat(desktop): add ARIA live-region & navigation semantics to the console UI

[ceilf6]

Linked Issue Or Context

Closes #348

Summary

Assistive technology could not perceive the console's dynamic surfaces. #344 added visual keyboard-focus rings and reduced-motion, but AT semantics were still missing. This PR adds purely-additive ARIA semantics — no behavior, layout, text, or styling changes:

• StatusPill — role="status" + aria-live="polite" so run-status transitions (planning → running → completed/failed) are announced; decorative beacon marked aria-hidden.
• EventStream log — role="log" + aria-live="polite" + aria-relevant="additions" + aria-label="遥测流" so streamed telemetry lines are announced as they append.
• App nav — aria-label="主导航" on the nav, aria-current="page" on the active item, decorative nav-dots marked aria-hidden.
• ApprovalDrawer — rendered as a labelled <section> (aria-label naming the pending tool) so the approve/reject surface is a named group.

Impact Scope

Renderer-only, leaf/near-leaf components. No store, IPC, or contract changes.

GitNexus Impact Summary

• Risk level: LOW
• Critical skeleton changes: none (renderer presentational components)
• GitNexus impact: detect_changes → exactly the 4 expected symbols touched (App, StatusPill, EventStream, ApprovalDrawer); 1 affected process App → Submit (step 1, App) — additive attributes only, no behavioral change. impact(upstream) on each = LOW (single parent caller, all flow into App).
• Verification: see below.

Verification

• biome check on all 4 files — clean.
• pnpm --filter @frontagent/desktop typecheck — clean.
• pnpm --filter @frontagent/desktop test — 13 files, 96 tests passing.

Design note on the ApprovalDrawer element

The issue suggested role="group" on the drawer, but biome's a11y/useSemanticElements rule (correctly) prefers a native semantic element over a role on a generic <div>, and aria-label is unsupported on a bare <span>. So the drawer is a native <section aria-label=…> (semantic, label-supported, no layout impact since .approval owns all styling, no biome-ignore needed), and the risk badge keeps its visible text (already announced inline) rather than an unsupported aria-label.

Note on tests

apps/desktop follows an established no-DOM-test architecture (no @testing-library/jsdom installed; logic lives in the store layer, components are not unit-tested). Per the repo-guard issue note, rather than introduce a DOM-testing stack (a much larger, convention-breaking change) for attribute assertions, verification relies on typecheck + biome's a11y ruleset + the contained additive diff. Happy to add a lightweight render assertion if maintainers want to adopt that stack.

Checklist

• I have linked an issue or explained why this PR stands alone.
• I have kept the diff focused on the stated change.
• I have run pnpm quality:precommit, or explained why it could not run.
• I have run pnpm quality:local for critical skeleton changes — N/A, not a critical skeleton change.
• I have updated docs or tests when behavior, public APIs, or Harness contracts changed — purely-additive ARIA, no behavior/API/contract change; test convention noted above.
• For critical skeleton changes, I have filled the GitNexus impact summary with concrete results — filled despite being non-critical.

🤖 Generated with Claude Code

[github-actions]

🛡️ ceilf6/repo-guard

代码评审报告: feat(desktop): add ARIA live-region & navigation semantics to the console UI

风险等级: 中
处理建议: 批准
决策摘要: ** 可以合并；变更仅触及 renderer 叶子组件的附加 ARIA 语义，关联 issue #348 的主要验收点已覆盖，剩余风险主要是缺少 DOM/AT 层面的自动断言。

级联分析

• 变更符号: 原始模型未提供结构化级联字段。
• 受影响流程: 原始模型未提供结构化级联字段。
• 变更集外调用方: unknown
• 置信度: degraded

问题发现

模型未返回可结构化的问题发现；已提取可用的决策字段，原始非契约内容未附在评论中。

行级发现

• 无明确变更行归属。

Karpathy 评审

• 假设: 模型输出需要归一化为固定 Markdown 契约。
• 简洁性: 已提取 summary、finding、evidence 与 fix；原始 prose 不再附在评论中，避免占用下游解析与代理上下文。
• 变更范围: 原始模型未提供结构化范围字段。
• 验证: 需要查看 CI、测试或人工 CR 证据补强合并信心。

缺失覆盖

• 输出未命中 Repo Guard Markdown 契约；建议补充真实模型质量评估覆盖。