fix: highlight the current docs section

[D3SOX]

Documentation pages show section links under “On this page,” but those links never highlight the section being read because the section tracker only runs on the Features page.

Add a docs section tracker that updates the existing active style and aria-current as the reader scrolls, follows anchors, or resizes the viewport. Keep the current guide highlighted and synchronize the mobile section picker.

Validation: 41 Bun tests pass, including seven section-tracking regression tests; strict TypeScript checks and the production build pass. The build uses the deployed image cache, matching CI. Desktop scrolling, direct anchors, mobile picker navigation, and non-ASCII fragment selection were verified in the browser.

Visual evidence: the existing docs page with this branch's compiled section tracker loaded into the browser; Linux is highlighted under “On this page” while the current guide remains highlighted.

Created by GPT-6.1-Sol using the Codex harness in T3 Code.

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📝 Walkthrough

Walkthrough

The docs layout now loads a client-side script that tracks the active table-of-contents section. The script updates navigation state and an optional jump select as the page scrolls or resizes.

Changes

Docs table-of-contents tracking

Layer / File(s)	Summary
Section tracking and layout integration src/scripts/docs-toc.ts, src/layouts/DocsLayout.astro, tests/docs-toc.test.ts	The layout loads the tracker. The tracker selects the active section from heading positions, updates navigation state and an optional jump select, and handles scroll and resize events. Tests cover initial and restored positions, scrolling, bottom-of-page selection, resize updates, animation-frame scheduling, and pages without matching targets.

Priority: ⬇️ Low

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

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant DocsLayout
  participant DocsToc as docs-toc script
  participant Window
  participant Headings
  participant Navigation
  DocsLayout->>DocsToc: Load client-side script
  DocsToc->>Headings: Resolve hash links to headings
  Window->>DocsToc: Send scroll or resize event
  DocsToc->>Headings: Find active section from scroll position
  DocsToc->>Navigation: Set is-active and aria-current
  DocsToc->>Navigation: Synchronize optional jump select

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Merge Risk: 🔵 Low · up to a85d2

Documentation with a non-ASCII section heading could lose its mobile picker selection. The current content is unaffected, so this is a bounded issue to fix or accept before merging.

🚥 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 5 functions across 2 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title clearly and concisely describes the main change: highlighting the current documentation section.
Description check	✅ Passed	The description directly explains the documentation section tracker, its behavior, validation, and visual evidence. It is related to the changeset.

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 5 functions across 2 files. (1 skipped: 1 unsupported.)

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[D3SOX]

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Actionable comments posted: 1

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🤖 Prompt to fix review comments

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Inline comments:
Review comments at @src/scripts/docs-toc.ts:
- Line 33: In the active-section selection logic in docs-toc.ts, assign the
picker value from active.getAttribute('href') rather than active.hash so it
matches the rendered link value, including for non-ASCII headings. Add a
native-DOM or browser test that verifies selection for a non-ASCII heading.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: e49a1bef-357b-48da-8ab9-726647ec72fb

📥 Commits

Reviewing files that changed from the base of the PR and between 3e0e13a and a85d2bf.

📒 Files selected for processing (3)

• src/layouts/DocsLayout.astro
• src/scripts/docs-toc.ts
• tests/docs-toc.test.ts

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