Add accessibility documentation for Layout sidebar row_placement: :none

[liuliu-dev]

What are you trying to accomplish?

Adds accessibility documentation warning about using row_placement: :none on the Layout component's sidebar as requested in https://github.com/github/accessibility-audits/issues/14738#issuecomment-3824258460

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• Low risk the change is small, highly observable, and easily rolled back.
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Accessibility

• Fixes axe scan violation - This change fixes an existing axe scan violation.
• No new axe scan violation - This change does not introduce any new axe scan violations.
• New axe violation - This change introduces a new axe scan violation. Please describe why the violation cannot be resolved below.

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Lookbook)
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

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[Copilot]

Pull request overview

This PR adds accessibility documentation to warn developers about potential WCAG 1.4.10 Reflow issues when using row_placement: :none on the Layout component's sidebar. The documentation clarifies that this setting hides the sidebar at narrow viewports, which could create accessibility problems if the sidebar contains essential content.

Changes:

• Added accessibility warning about row_placement: :none to the main Layout component documentation
• Updated the row_placement parameter description to include the same accessibility warning

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
app/components/primer/alpha/layout.rb	Added accessibility documentation in both the component-level accessibility section and the sidebar parameter description
static/info_arch.json	Updated the corresponding JSON metadata with the same accessibility documentation

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[Copilot]

The documentation text differs slightly between the two locations. In this file, it says "WCAG 1.4.10 Reflow issues" while in layout.rb it says "WCAG 1.4.10 Reflow failures". These should use consistent terminology. Consider using "failures" in both places to be more technically accurate.

Suggested change

	"description": "Sidebar placement when `Layout` is in row mode. One of `:end`, `:none`, or `:start`. **Note:** Using `:none` hides the sidebar at narrow viewports, which may cause WCAG 1.4.10 Reflow issues if the sidebar contains essential content."
	"description": "Sidebar placement when `Layout` is in row mode. One of `:end`, `:none`, or `:start`. **Note:** Using `:none` hides the sidebar at narrow viewports, which may cause WCAG 1.4.10 Reflow failures if the sidebar contains essential content."