docs: add guide for MCP Apps integration in A2UI surface

[sugoi-yuzuru]

Description

Add a guide for MCP Apps integration into A2UI Surfaces.

Pre-launch Checklist

• I signed the CLA.
• I read the Contributors Guide.
• I read the Style Guide.
• I have added updates to the CHANGELOG.
• I updated/added relevant documentation.
• My code changes (if any) have tests.

If you need help, consider asking for advice on the discussion board.

[gemini-code-assist]

Code Review

This pull request introduces a new guide for MCP Apps integration in A2UI surfaces, detailing the double-iframe isolation pattern, security rationale, and providing usage examples and testing instructions. Feedback includes a suggestion to simplify the input binding logic in the documentation's code examples using the nullish coalescing operator and a recommendation to align the navigation title in mkdocs.yaml with the document's main heading for consistency.

[gemini-code-assist]

The inputBinding logic for content and title can be simplified using the nullish coalescing operator (??). This improves readability and conciseness, and explicitly handles cases where the property might be null by converting it to undefined, aligning with common Angular input binding patterns.

For example, ('content' in properties && properties['content']) || undefined can be replaced with properties['content'] ?? undefined.

Suggested change

	inputBinding(
	'content',
	() => ('content' in properties && properties['content']) || undefined,
	),
	inputBinding('title', () => ('title' in properties && properties['title']) || undefined),
	],
	},
	inputBinding(
	'content',
	() => properties['content'] ?? undefined,
	),
	inputBinding('title', () => properties['title'] ?? undefined),

[gemini-code-assist]

The navigation entry title "MCP Apps integration in A2UI Surface" is inconsistent with the document's main heading "# MCP Apps Integration in A2UI Surfaces". For better consistency and user experience, it's recommended to align the navigation title with the document's actual title.

      - MCP Apps Integration in A2UI Surfaces: guides/mcp-apps-in-a2ui-surface.md

[wrenj]

mcp apps in a2ui surfaces