fix: 优化用户交互文案，为错误消息添加可操作提示

- 为 budget/turns/structured-output 三种错误消息添加 Tip 提示，指导用户如何继续
- Onboarding 安全步骤标题从 "Security notes" 改为更友好的 "Before you start, keep in mind"
- Trust Dialog 精简为两句核心信息，降低认知负荷
- 新增 7 个测试验证消息内容包含关键引导信息

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/QueryEngine.ts

@@ -1051,7 +1051,9 @@ export class QueryEngine {
             initialAppState.fastMode,
           ),
           uuid: randomUUID(),
-          errors: [`Reached maximum budget ($${maxBudgetUsd})`],
+          errors: [
+            `Reached maximum budget ($${maxBudgetUsd}). Increase the limit with --max-budget-usd or start a new session.`,
+          ],
         }
         return
       }