aifirst: lift context/agents/tools runtime to lib-aifirst-ui

The mechanism (context surface registry, persona storage + hooks, tool
parser/dispatcher) is now generic and lives in @crema/aifirst-ui/{context,
agents,tools}. This template keeps only the arcadia-shaped configuration:

- agents.ts — owns DEFAULT_AGENTS + legacy/retired migration sets, calls
  configureAgents() at module load, re-exports the runtime
- admin-tools.ts — keeps the 19 arcadia tool definitions, binds the
  runtime via createToolRuntime(TOOLS), re-exports the bound functions
- admin-context.ts — deleted; 18 routes now import directly from
  @crema/aifirst-ui/context

Routes that import from ~/lib/agents and ~/lib/admin-tools are unchanged
(wrapper modules preserve the existing import surface).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/routes/users.tsx

@@ -87,7 +87,7 @@ import {
 } from "~/lib/arcadia/users"
 import { pageTitle } from "~/lib/page-meta"
 import { useSession } from "~/lib/session"
-import { useRegisterAdminContext } from "~/lib/admin-context"
+import { useRegisterContext } from "@crema/aifirst-ui/context"
 import { UserDetailSheet } from "~/components/users/user-detail-sheet"
 
 export const meta = () => pageTitle("Users")
@@ -167,7 +167,7 @@ export default function UsersRoute() {
     }),
     [users, invitations, roles],
   )
-  useRegisterAdminContext("users", summary)
+  useRegisterContext("users", summary)
 
   return (
     <AppShell>