chore: Add --system flag for existing agents + update system prompt variable names (#328)

src/agent/create.ts

@@ -53,7 +53,7 @@ export async function createAgent(
   skillsDirectory?: string,
   parallelToolCalls = true,
   enableSleeptime = false,
-  systemPrompt?: string,
+  systemPromptId?: string,
   initBlocks?: string[],
   baseTools?: string[],
 ) {
@@ -202,13 +202,13 @@ export async function createAgent(
   const modelUpdateArgs = getModelUpdateArgs(modelHandle);
   const contextWindow = (modelUpdateArgs?.context_window as number) || 200_000;
 
-  // Resolve system prompt (ID, subagent name, or literal content)
-  const resolvedSystemPrompt = await resolveSystemPrompt(systemPrompt);
+  // Resolve system prompt ID to content
+  const systemPromptContent = await resolveSystemPrompt(systemPromptId);
 
   // Create agent with all block IDs (existing + newly created)
   const agent = await client.agents.create({
     agent_type: "letta_v1_agent" as AgentType,
-    system: resolvedSystemPrompt,
+    system: systemPromptContent,
     name,
     description: `Letta Code agent created in ${process.cwd()}`,
     embedding: embeddingModel,