Put token limits on sessions

### Feature summary

Allow users to place token limits on their sessions to prevent overspending

### What problem are you trying to solve?

Long-running agent sessions can easily use up an entire month of AI credits when unsupervised. This would be solved by placing token limits on sessions allowing users to put a cap on the maximum amount of _non-cached_ tokens used.

### Proposed solution

_No response_

### Workflow impact

_No response_

### Installation context

_No response_

### Additional context

_No response_

该 issue 未指定文件、测试或入口点；首先定位 session 和非缓存 token 使用量的路径。定义用户如何配置 session 上限、何时测量使用量，以及达到上限时会发生什么。范围和强制执行行为得到明确规定并由适当的测试覆盖后，即视为完成。

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