[Server][Capability][Examples] SEP-1865 MCP Apps: Link tools to UI templates via attribute metadata + example/inspector tests #352

Implements the tool↔UI linkage and example coverage for SEP-1865 (MCP Apps) for the MCP Spec 2026-07-28 release.

Tracked by umbrella #335.

PHP SDK changes

• Extend #[McpTool] (or add a sibling attribute) to declare which ui:// template a tool's result should render in.
• Update the tool result formatter in src/Capability/Formatter/ to emit the linkage metadata in tools/call responses per the spec wire format.
• Add examples/server/apps/ walkthrough: a tool that returns structured data plus a ui:// template that renders it.
• Inspector tests verifying the wire format end-to-end.

Related

• Umbrella [2026-07-28] Extensions framework + Tasks + MCP Apps #335
• Depends on SEP-1865 schema + SEP-1865 builder sub-issues