fix: respect toolsEnabled config for CLI backends [AI-assisted]

Add `toolsEnabled` option to `CliBackendConfig` that controls whether
the "Tools are disabled" system prompt is injected for CLI backends.

When `toolsEnabled: true`, the backend is assumed to have its own tool
handling (e.g., Claude CLI with --allowedTools), so we skip the
misleading "Tools are disabled" message.

Default behavior is unchanged (toolsEnabled defaults to false).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/agents/cli-runner.ts

@@ -65,7 +65,8 @@ export async function runCliAgent(params: {
 
   const extraSystemPrompt = [
     params.extraSystemPrompt?.trim(),
-    "Tools are disabled in this session. Do not call tools.",
+    // Only add "tools disabled" message if tools aren't enabled for this backend
+    backend.toolsEnabled ? undefined : "Tools are disabled in this session. Do not call tools.",
   ]
     .filter(Boolean)
     .join("\n");

src/config/types.agent-defaults.ts

@@ -89,6 +89,8 @@ export type CliBackendConfig = {
   imageMode?: "repeat" | "list";
   /** Serialize runs for this CLI. */
   serialize?: boolean;
+  /** Whether tools are enabled for this CLI backend (default: false). */
+  toolsEnabled?: boolean;
 };
 
 export type AgentDefaultsConfig = {