fix: show source load errors instead of stale success state

[Gaubee]

Summary

• treat source fetch errors as error state even when cached payload fallback exists
• render source status with error-first priority in settings list (red icon + error copy)
• add regression test for cache-fallback-on-failure path
• include latest vite config update for om-hub remote source
• ignore generated miniapps/om-hub/ directory

Validation

• pnpm vitest run src/services/ecosystem/tests/registry.test.ts
• pnpm exec oxlint src/services/ecosystem/registry.ts src/stackflow/activities/SettingsSourcesActivity.tsx src/services/ecosystem/tests/registry.test.ts vite.config.ts
• pnpm agent review verify (fails on existing unrelated unit-test baseline in repo)