Expand test coverage across server, agent, and web; fix bugs found during audit.

Adds hundreds of unit/integration/e2e tests, fixes WS bcrypt auth, config merge, fleet analytics, agent schedule/log tail, and documents stale PROBLEMS items. Updates PROBLEMS.md, README, and test scripts; ignores local spread-kits and coverage dirs.

server/web/src/App.tsx

@@ -13,7 +13,7 @@ const SettingsPage = lazy(() => import('./pages/SettingsPage'));
 const GuidePage = lazy(() => import('./pages/GuidePage'));
 const CruciblePage = lazy(() => import('./pages/CruciblePage'));
 
-function PageFallback() {
+export function PageFallback() {
   return (
     <div className="session-gate" style={{ minHeight: '40vh' }}>
       <p className="font-tech">Loading…</p>