🎨 Palette: Add accessible table headers and caption to telemetry timeline

[igor-holt]

💡 What

Added a visually hidden <caption> element to the telemetry data table and appended scope="col" to the table header cells (<th>). Added a journal entry detailing the approach for hiding elements visually without utility classes.

🎯 Why

Screen-reader users had no context for the data table and no explicit association between column headers and data cells, causing a confusing navigational experience.

♿ Accessibility

• Provides table context via an accessible <caption> tag.
• Associates headers directly with the corresponding data via scope="col".
• Since global .sr-only utility classes do not exist in this repo, explicitly styled the caption with inline CSS to guarantee accessibility while preserving visual layout.

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PR created automatically by Jules for task 4271447472720523932 started by @igor-holt

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[Copilot]

Pull request overview

This PR improves the accessibility of the telemetry timeline’s raw data table by adding proper table semantics for screen readers.

Changes:

• Added an accessible (visually hidden) <caption> to provide context for the telemetry details table.
• Added scope="col" to <th> elements to explicitly associate column headers with their cells.
• Added a short journal entry documenting the visually-hidden styling approach in the absence of a global utility class.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
components/TelemetryTimeline.tsx	Adds a visually hidden table caption and explicit column header scoping for improved screen-reader navigation.
.Jules/palette.md	Documents the visually-hidden pattern used due to the lack of a global .sr-only utility in this repo.

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[gemini-code-assist]

Code Review

This pull request improves the accessibility of the TelemetryTimeline component by adding a descriptive table caption and defining column scopes for headers. It also updates the project's documentation to include a pattern for visually hiding elements. Review feedback recommends replacing the deprecated clip CSS property with clipPath: 'inset(50%)' and suggests centralizing these styles into a reusable .sr-only utility class in globals.css to improve maintainability and keep the JSX clean.

[gemini-code-assist]

Recommending a verbose inline style for a common utility like 'visually hidden' content is suboptimal for maintainability. It is better to add a .sr-only utility class to app/globals.css once and reuse it across the project. This centralizes the logic and keeps the JSX clean. Additionally, the clip property is deprecated; clipPath: 'inset(50%)' is the modern standard.

Suggested change

**Action:** When a screen-reader element needs to be visually hidden without breaking layout and no utility class exists, apply an explicit inline style pattern instead: `style={{ position: 'absolute', width: '1px', height: '1px', padding: 0, margin: '-1px', overflow: 'hidden', clip: 'rect(0, 0, 0, 0)', whiteSpace: 'nowrap', borderWidth: 0 }}`. This ensures accessibility guidelines are met within the constraints of the project architecture.

**Action:** When a screen-reader element needs to be visually hidden, the preferred approach is to add a .sr-only utility class to app/globals.css. If inline styles must be used, apply a consistent pattern that avoids deprecated properties: style={{ position: 'absolute', width: '1px', height: '1px', padding: 0, margin: '-1px', overflow: 'hidden', clipPath: 'inset(50%)', whiteSpace: 'nowrap', border: 0 }}. This ensures accessibility guidelines are met while maintaining code quality.

[gemini-code-assist]

The clip property is deprecated in favor of clip-path. For better future-proofing, use clipPath: 'inset(50%)'. Furthermore, using inline styles for this common pattern is hard to maintain. Consider adding a .sr-only class to app/globals.css instead.

Suggested change

	<caption style={{ position: 'absolute', width: '1px', height: '1px', padding: 0, margin: '-1px', overflow: 'hidden', clip: 'rect(0, 0, 0, 0)', whiteSpace: 'nowrap', borderWidth: 0 }}>
	<caption style={{ position: 'absolute', width: '1px', height: '1px', padding: 0, margin: '-1px', overflow: 'hidden', clipPath: 'inset(50%)', whiteSpace: 'nowrap', border: 0 }}>