refactor: remove core-ui from main (scaffoldable via gen core-package ui)

Removal across all three consumers:
- apps/storybook: strips @repo/core-ui dep, clears stories glob (now []),
  removes globals.css import from preview.ts
- apps/web-next: strips @repo/core-ui dep + transpilePackages entry
- apps/web-tanstack: strips @repo/core-ui dep
- packages/core-ui: deleted entirely (28 files)

No app pages needed surgery — neither web-next nor web-tanstack source
files imported @repo/core-ui directly. The storybook app referenced it
only via the stories glob and the globals.css preview import.

Gates: 40/40 tasks successful, all 4 e2e byte-identical reconstructions
pass (realtime, events, trpc, ui).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web-tanstack/package.json

@@ -15,7 +15,6 @@
     "@repo/blog": "workspace:*",
     "@repo/core-api": "workspace:*",
     "@repo/core-shared": "workspace:*",
-    "@repo/core-ui": "workspace:*",
     "@repo/marketing-pages": "workspace:*",
     "@repo/navigation": "workspace:*",
     "@sentry/node": "^10.52.0",