fix(a11y): provide a non-empty page label for filesystem roots

[seonghobae]

Accessibility problem

Java File.getName() returns an empty string for filesystem roots. Rendering that value directly produces an empty document <title> and <h1>, removing the generated page's visible and programmatic location label.

Proposed bounded repair

• derive one escaped display label per directory;
• use the directory name when non-empty;
• use the absolute root path only when the name is empty; and
• reuse the same label in <title> and the page's <h1>.

Current status

This branch overlaps the same HTML template changed by canonical CSP PR #363 and is intentionally not merge-ready. After #363 integrates, this PR must be rebuilt or updated on the protected master without reverting the exact style-byte/CSP contract.

Before returning to ready-for-review it must also:

1. remove duplicated conditional rendering by introducing one clearly named display-label value;
2. prove the behavior through the real generated-file path, including HTML escaping of a fallback path;
3. preserve ordinary non-root directory labels;
4. add beginner-readable KDoc where production API is introduced;
5. add CHANGELOG.md and APA 7 doctoring grounded in current HTML/WCAG primary guidance without claiming formal conformance; and
6. pass exact-current-head CI, JaCoCo statement/branch coverage, Security Scan, Semgrep, current-head automated review, and independent non-author approval.

Queued, pending, skipped-required, cancelled, absent, stale-head, or failed checks are not success. Duplicate root-label PR checks and reviews are not reusable.

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📥 Commits

Reviewing files that changed from the base of the PR and between a3c445e and 6274f00.

📒 Files selected for processing (3)

• .jules/palette.md
• src/main/kotlin/html4tree/main.kt
• src/test/kotlin/html4tree/MainTest.kt

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