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

README.md

@@ -70,6 +70,13 @@ holds a per-app gateway token, never a real Anthropic key, and the route refuses
 anonymous requests and caps each account at roughly 20 requests an hour. The
 platform's monthly AI cap is the backstop.
 
+There's no chat: the AI is briefed from the same keywords box and Style chip
+as the built-in generator (`src/lib/ai-prompt.ts` is the rulebook), and its
+names are merged in front of the built-in list, tagged **AI**, and checked like
+everything else. When AI is on, a **Tell the AI more** field appears — tone,
+words to include or avoid, audience — which is appended to that brief (capped
+at 300 chars, enforced client- and server-side). The built-in generator ignores it.
+
 Sign-in is OTM SSO: `/sso/authorize?aud=app:names` on the control plane hands
 back a 60-second single-use ticket to `/api/auth/otm-sso`, which mints a small
 HMAC-signed cookie (`names.session`). There are no user accounts in this app.