/claim #1301

Summary

Integrate MCP-UI support into Archestra platform — when MCP servers return tool results containing UIResource, the Chat UI renders them as rich interactive HTML in sandboxed iframes instead of showing raw JSON.

Changes

Shared Types (shared/mcp-ui.ts)

• McpUiResource, McpUiMeta, McpUiMimeType types
• extractMcpUiResourceUri() — extracts _meta.ui.resourceUri from tool output
• extractInlineMcpUiResource() — extracts inline UIResource from MCP content arrays
• 12 unit tests covering JSON/object parsing and edge cases

Frontend — Chat UI

• McpUiRenderer component: sandboxed iframe (allow-scripts only) with auto-resize via postMessage, supports text/html, text/uri-list, and remote-dom MIME types
• MessageTool modified: detects UIResource in tool results and renders via McpUiRenderer instead of raw ToolOutput`

MCP Gateway

No changes needed — tool results already pass through as-is, preserving _meta and resource content.

Vendor MCP-UI Wrappers (for catalog)

• GitHub wrapper: list_repos, view_pull_request, search_issues — dark-themed HTML tables with repo stats, PR diffs, and label rendering
• Weather wrapper: get_weather, get_forecast — gradient weather cards with mock data fallback for demos

Verification

• ✅ 12/12 unit tests pass
• ✅ TypeScript type-check clean
• ✅ Biome lint clean (0 errors)
• ✅ Backward compatible — existing tool output renders identically when no UIResource is present

Closes #1301