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/ai.tsx

@@ -101,7 +101,7 @@ import {
   subscribeActiveReasoning,
   type ReasoningEffort,
 } from "~/lib/arcadia/llm-configs"
-import { formatAdminContextForPrompt } from "~/lib/admin-context"
+import { formatContextForPrompt } from "@crema/aifirst-ui/context"
 import { ConfirmCard } from "~/components/assistant/confirm-card"
 import { renderToolResult } from "~/components/assistant/tool-result-renderers"
 
@@ -722,7 +722,7 @@ function ChatSurface({
     ARCADIA_KNOWLEDGE,
     persona,
     handoffNote,
-    formatAdminContextForPrompt(),
+    formatContextForPrompt(),
   ]
     .filter(Boolean)
     .join("\n\n")