feat(agents): change orchestrator-sisyphus default model to claude-sonnet-4-5

- Update orchestrator-sisyphus model from opus-4-5 to sonnet-4-5 for better cost efficiency
- Keep Prometheus using opus-4-5 for planning tasks

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/agents/orchestrator-sisyphus.ts

@@ -1442,7 +1442,7 @@ export function createOrchestratorSisyphusAgent(ctx?: OrchestratorContext): Agen
     description:
       "Orchestrates work via sisyphus_task() to complete ALL tasks in a todo list until fully done",
     mode: "primary" as const,
-    model: "anthropic/claude-opus-4-5",
+    model: "anthropic/claude-sonnet-4-5",
     temperature: 0.1,
     prompt: buildDynamicOrchestratorPrompt(ctx),
     thinking: { type: "enabled", budgetTokens: 32000 },