Add ASCII logo, spinner during install, all packages core, fix tests

- ASCII art logo on website hero and OAuth callback page
- Clean spinner during postinstall instead of npm noise
- pi-session-search and pi-memory moved to core (13 packages)
- pi-generative-ui is the only optional package
- Alpha Hub callback page branded with Feynman logo

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@companion-ai/feynman",
-  "version": "0.2.6",
+  "version": "0.2.7",
   "description": "Research-first CLI agent built on Pi and alphaXiv",
   "type": "module",
   "engines": {