feat: 'Tell the AI more' free-text brief for AI names (v0.5.0)

Appended to the shared prompt (lib/ai-prompt.ts) on both AI paths; capped at
300 chars client- and server-side; shown only when AI is on; kept in
sessionStorage so it survives 'Show me more'.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XStQKxPfEjrTvWo83KFCxG

package.json

@@ -1,6 +1,6 @@
 {
   "name": "names-poweredbyotm",
-  "version": "0.4.1",
+  "version": "0.5.0",
   "private": true,
   "scripts": {
     "dev": "next dev --port 3000",