cb3df51f08
First pass of the web UI design doc from the M1 close-out brainstorm. Covers the stack (SvelteKit static + Go embed), auth model (cookie + bearer from one endpoint), /api/* surface, shell layout (sidebar + bottom player), first-cut feature scope, and how later web UI work threads into M2–M5 alongside each backend milestone instead of landing as a post-hoc M6. Also ignores the local .superpowers/ brainstorming companion cache. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>