Replace the Kanban generated-slot unit test's inline raw HTML board payload with a hemplate-rendered view and DOM-aware assertion.
req: html_safety/002
req: view/001
req: test/005
Move the kanban SSE presence fragment from Rust raw HTML formatting into a hemplate partial/view and cover the rendered structure with scraper.
req: html_safety/002
req: view/001
req: test/005