chore: add Experimental Editor link to docs header + legal footer

[Mossaka]

Summary

• Add italic+dashed-border "Experimental Editor" link to the docs top navigation bar, pointing to /editor/
• Replace single Terms of Service footer link with three official GitHub legal links (Terms · Privacy · Security)

Test plan

• Verified make build-docs — Astro build succeeds (pre-existing broken internal links from starlight-links-validator are unrelated)
• Visual check: header shows "Experimental Editor" with dashed border + italic style
• Visual check: footer shows Terms · Privacy · Security links with correct URLs

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR enhances the documentation site's navigation and footer by adding an experimental editor link and updating legal footer links to official GitHub policy pages.

Changes:

• Adds "Experimental Editor" navigation link with italic styling and dashed border to indicate experimental status
• Replaces single GitHub Next Terms of Service link with three official GitHub legal links (Terms, Privacy, Security)
• Adds styling for legal separator dots with theme-aware colors

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
docs/src/components/CustomHeader.astro	Adds experimental editor link to navigation bar with italic+dashed styling
docs/src/components/CustomFooter.astro	Replaces single Terms link with three official GitHub legal links and adds separator styling

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[Copilot]

The experimental-link border style may not be visible enough in light theme. The border color rgba(110, 118, 129, 0.4) is designed for dark backgrounds. Consider adding a light theme variant using :global([data-theme='light']) .experimental-link with a darker border color (e.g., rgba(110, 118, 129, 0.6) or a similar color to what's used elsewhere in the codebase for light theme borders).

Suggested change

	}
	}
	:global([data-theme='light']) .experimental-link {
	border-color: rgba(110, 118, 129, 0.6);
	}

[Copilot]

The 1px dashed border added to .experimental-link will make this link element 2px taller than other header links (1px top + 1px bottom). Consider adjusting the padding to compensate, for example by reducing top/bottom padding to maintain consistent alignment with other header links. This could be achieved by overriding the padding in .experimental-link to something like 'padding: calc(0.25rem - 1px) 0.75rem;' to account for the border.

Suggested change

	border: 1px dashed rgba(110, 118, 129, 0.4);
	border: 1px dashed rgba(110, 118, 129, 0.4);
	padding: calc(0.25rem - 1px) 0.75rem;