fix: add keyboard-equivalent treemap navigation

[seonghobae]

Purpose

Make the disk treemap operable and understandable without a pointing device while preserving the existing pointer visualization and navigation authority. The native equivalent now remains keyboard-scrollable even when a folder contains only files and tells the customer what to do when no entries are available.

Exact current state

• Exact source head: d2bf5e5d2344bb33327491c16862031c4a7daa20.
• Live protected main: be418bac9bfbdc8aa41b1a698713833e3dbccfdc.
• The PR is open, Ready for review, mergeable, and based directly on protected main.
• Current semantic delta remains exactly src/lib/Treemap.svelte plus src/lib/treemapAccessibilityContract.test.ts.
• Current-head formal reviews and review threads are empty; no approval is claimed.

Test-first accessibility repair

• RED head 0ac1b50d4634c18e5d9de55d0d10c4fceed09ab4 required a native keyboard-equivalent surface while protected main exposed navigation only through the pointer canvas.
• Initial implementation 3fde380f7b7df0f68b8e049a32563c6fd03822d4 kept treemap drawing/click geometry unchanged, marked the pointer canvas assistive-technology-hidden, and added a native <details>/list alternative over the same node.entries with normal directory buttons invoking only onOpen(entry.path).
• Review then found that the alternative list itself had a 14rem overflow boundary but no sequential focus target when a folder contained files only, and an empty node rendered a blank list without a next action.
• Test-only commit 72c262a53b2aa3156d19a4bad3c3f085b723fcce requires a named focusable overflow region, visible keyboard focus, action-oriented directory labels, an entry count, and an empty-state recovery instruction.
• Current implementation d2bf5e5d2344bb33327491c16862031c4a7daa20 moves overflow to a role="region", tabindex="0" wrapper, adds a focus-visible outline, labels directory rows as 폴더 열기, reports the entry count in the native summary, and tells the customer to move to the parent folder or scan another folder when no entries exist.

Scan data, path authority, filesystem mutation, treemap geometry, pointer navigation, and directory-open authority remain unchanged. File entries remain descriptive rather than becoming mutation controls.

Standards boundary

This is a narrow WCAG 2.2 non-text-content and keyboard-operability repair using native HTML controls and a named scroll region rather than synthetic canvas keyboard behavior.

Exact-head validation

For exact head d2bf5e5d2344bb33327491c16862031c4a7daa20:

• Test 31885078411 — queued;
• Release 31885078364 — pending;
• Security Scan 31885078282 — queued;
• SAST Semgrep 31885078288 — queued.

Queued or pending evidence is not passing, and predecessor-head success does not transfer. Conditional PR-inapplicable publication or attestation helpers are not represented as passing release or provenance evidence.

Scope / non-duplication

This line owns only src/lib/Treemap.svelte and its focused accessibility contract. It does not modify src/routes/+page.svelte owned by #202, TopFiles #203, repository-wide exact coverage #156, canonical documentation #149, or any cleanup/cloud/provider authority line.

Remaining integration blockers

• The live organization ruleset requires one independent approving review, approval after the last push, and review-thread resolution; the current head has no approval.
• Repository-wide exact 100% owned-production region/statement-equivalent, branch, function, and line coverage remains materially unsatisfied on canonical owner ci: require exact-head production coverage evidence #156.
• Ready-for-review status is not merge authorization.

Required before merge

Do not merge unless the unchanged exact head satisfies every applicable live required workflow and current finding, every review thread is resolved, a qualifying independent approval covers the last push/current head, fresh protected-main ancestry remains current, the live review ruleset is satisfied, and repository-wide exact coverage is satisfied without exclusions or threshold weakening. Pending, queued, skipped-required, neutral-required, failed, stale, predecessor, synthetic, diagnostic-only, status-only, model-only, rate-limited, no-source scanner, or infrastructure-only evidence is not passing.

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Summary by CodeRabbit

• 접근성 개선
  • 트리맵 아래에 키보드로 탐색할 수 있는 접근 가능한 트리 뷰를 추가했습니다.
  • 디렉터리는 버튼으로 열 수 있고, 파일명과 크기를 확인할 수 있습니다.
  • 빈 목록에는 다음 행동을 안내하는 메시지를 표시합니다.
  • 시각적 캔버스와 항목 목록을 구분해 보조 기술이 더 쉽게 탐색할 수 있습니다.

[coderabbitai]

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Review configuration:

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 0c869e67-bac1-4b9b-a6a0-1e3f12014bd5

📥 Commits

Reviewing files that changed from the base of the PR and between 0cab9bf and d9fa06f.

📒 Files selected for processing (2)

• src/lib/Treemap.svelte
• src/lib/treemapAccessibilityContract.test.ts

📝 Walkthrough

Walkthrough

Treemap.svelte에 캔버스 아래 접근성 트리를 추가했습니다. 폴더는 버튼으로 열고 파일은 이름과 크기로 표시합니다. 빈 상태와 키보드 스크롤을 지원하며, 관련 접근성 계약 테스트를 추가했습니다.

Changes

Treemap 접근성

Layer / File(s)	Summary
접근성 트리 렌더링과 스타일 src/lib/Treemap.svelte	캔버스를 aria-hidden="true"로 설정했습니다. <details>와 <summary> 기반 트리에 폴더 열기 버튼, 파일 이름·크기, 빈 상태를 추가했습니다. 목록 스크롤과 포커스 스타일도 추가했습니다.
접근성 계약 검증 src/lib/treemapAccessibilityContract.test.ts	접근성 트리 구조, 키보드 탐색, 폴더 열기 레이블, 파일 목록 스크롤, 포커스 스타일 및 빈 상태 안내를 검증합니다.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: 🟡 Moderate · up to 0cab9

The change adds a second keyboard-accessible list for entries that are already exposed elsewhere, which can create duplicate content and conflicting interaction paths for keyboard and assistive-technology users. Merge should wait until one canonical accessibility surface is retained.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	제목은 Treemap에 키보드 동등 탐색 표면을 추가하는 변경 사항을 정확하고 간결하게 설명합니다.
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/treemap-keyboard-alternative-v1

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[seonghobae]

Closing this line as stale/duplicative against the current product composition rather than merging a second navigation authority.

On live main (be418bac9bfbdc8aa41b1a698713833e3dbccfdc), src/routes/+page.svelte already renders the same node.entries immediately after <Treemap> as the canonical native <ul class="entries">; directories are native buttons that call the same open(e.path) path-navigation authority. This PR's current head d2bf5e5d2344bb33327491c16862031c4a7daa20 adds another complete list and another set of directory controls over that same collection, so merging it would duplicate semantics/actions and create two UI authorities.

The remaining narrow concern—keyboard scrolling when the canonical list contains only non-focusable file rows—belongs with the existing .entries surface in src/routes/+page.svelte, which is currently owned by #202, not with a second list inside Treemap.svelte. That should be repaired test-first on the canonical surface after the active owner is stable. Current-head Test/Release/Security/SAST are green, but those checks do not make a redundant UI change desirable or merge-authorized.