feat(tui): rebuild overview snapshot as donut-chart sections

[makoMakoGo]

What

Rebuilds the Overview tab's Snapshot panel as three sections with donut charts, replacing the previous text-only layout:

• Left — metric groups joined by dashed separators, plus a new Active Days row (days with >0 tokens, matching the footer's day count)
• Middle — Tokens donut (center shows total tokens) with a legend of colored markers, exact values, and per-segment percentages
• Right — Sources donut (center shows source health %) with a per-state legend (Clean/Degraded/Partial/Failed/Rejected)

Sections are split by vertical dividers with uniform 1-cell padding on both sides.

How

• New DonutChart widget (crates/tokscale-cli/src/tui/ui/donut.rs): braille dot-matrix ring (2x4 dots per cell, true circle in dot space), segments laid out clockwise from 12 o'clock, center text on a cleared background, and an empty_color ring when all weights are zero.
• Minimum visible arc: non-zero segments smaller than ~4 dots on the mid-band circumference are bumped to stay visible, funded proportionally from larger segments (sum stays 1). Zero-weight segments stay invisible by design; legends always carry the exact values.
• Progressive width tiers: ≥110 cols → all three sections; ≥80 → metrics + Tokens; ≥40 → metrics only; below → stacked text fallback.
• Colors: Cache Read / Clean follow theme.accent. Cache Write (LightBlue) and Partial (LightMagenta) use fixed colors because most themes set accent to cyan or near-cyan, which previously made those arcs and legend markers indistinguishable. Segment colors are shared between donut and legend via single token_buckets/source_buckets definitions.

Out of scope (unchanged): the data pipeline, the Tokens-per-Day chart above the panel, and the footer.

Verification

• cargo test -p tokscale-cli — 845 tests pass, including 15 new DonutChart tests and 15 rewritten panel tests (tiers, dividers, separators, overflow policy, segment colors, tiny-arc visibility, all-clean ring stays single-colored)
• cargo clippy, cargo fmt — clean
• Manual TUI runs at 200x50 / 95x40 / 60x40 against real data, plus a fabricated fixture with degraded/partial/failed sources to verify the multi-color Sources ring end to end

Summary by CodeRabbit

• 新功能
  • 概览快照新增 Tokens 与 Sources 环形图，直观展示数据分布及占比。
  • 环形图支持中心文字、颜色图例、空数据状态和尺寸自适应。
• 界面改进
  • 概览面板根据窗口宽度自动切换三列、两列、单列及窄屏布局。
  • 新增 Active Days 指标、竖向分隔线，并优化指标与图例的对齐、截断和显示效果。
• 稳定性
  • 优化极小窗口和不同面板尺寸下的显示，避免布局异常。

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: e1fce901-dc41-428d-a97d-153e40e7ec8b

📥 Commits

Reviewing files that changed from the base of the PR and between 03b3e1d and 8bf6d73.

📒 Files selected for processing (1)

• crates/tokscale-cli/src/tui/ui/overview_snapshot.rs

Walkthrough

Changes

概览甜甜圈图

Layer / File(s)	Summary
甜甜圈图组件 crates/tokscale-cli/src/tui/ui/donut.rs	新增基于 Unicode Braille 的甜甜圈图，支持分段颜色、最小可见弧、中心文本、背景和半径配置，并覆盖多种几何与边界测试。
概览面板布局接入 crates/tokscale-cli/src/tui/ui/mod.rs, crates/tokscale-cli/src/tui/ui/overview_snapshot.rs	将甜甜圈图接入 Overview Snapshot，重写三列、两列、单列和窄屏回退布局，新增指标、图例及分隔线渲染。
布局与视觉行为验证 crates/tokscale-cli/src/tui/ui/overview_snapshot.rs	新增布局定位、颜色提取和主题测试，验证分隔线、图例对齐、健康分段、指标裁剪及多尺寸渲染稳定性。

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Snapshot
  participant DonutChart
  participant Buffer
  Snapshot->>Snapshot: 根据可用宽度选择布局
  Snapshot->>DonutChart: 创建 Tokens 或 Sources 图表
  DonutChart->>Buffer: 绘制 Braille 环与中心文本
  Snapshot->>Buffer: 绘制指标、图例和分隔线

Loading

Possibly related PRs

• makoMakoGo/tokscale#154：引入了 Overview Snapshot 的渲染结构，与本次面板布局重构存在代码层面的关联。

Poem

小兔画环点点亮，
Braille 花瓣绕中央。
Tokens、Sources 排成行，
分隔虚线守两旁。
窄屏也能稳稳唱。

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	标题准确概括了将 Overview Snapshot 重构为甜甜圈图分区的主要改动。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/overview-snapshot-donuts

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[chatgpt-codex-connector]

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Reviewed commit: 03b3e1d5ea

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@crates/tokscale-cli/src/tui/ui/overview_snapshot.rs`:
- Around line 443-452: Update source_buckets so the donut chart contains only
source-level counts: Clean, Degraded, Partial, and Failed. Remove
rejected_records from the returned segments and adjust the array size and any
dependent rendering code accordingly; display rejected records separately if the
existing UI requires them.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 5d8763e9-aad5-4265-90ec-9d3057c88649

📥 Commits

Reviewing files that changed from the base of the PR and between 1e38ad3 and 03b3e1d.

📒 Files selected for processing (3)

• crates/tokscale-cli/src/tui/ui/donut.rs
• crates/tokscale-cli/src/tui/ui/mod.rs
• crates/tokscale-cli/src/tui/ui/overview_snapshot.rs

[codspeed-hq]

Merging this PR will not alter performance

✅ 41 untouched benchmarks

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_{Comparing feat/overview-snapshot-donuts (8bf6d73) with personal/local-clients (1e38ad3)}