Too many MCP servers results in continuous compaction

### Describe the bug

The CLI agent can end up in a degenerate state when you enable too many MCP servers that expand past the available context window of the model in question supporting the harness.

The CLI should detect this state and warn the user. In my case, I ended up with 94k / 128k context window consumed by tools

### Affected version

GitHub Copilot CLI 1.0.37.

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

Start by tracing how the CLI loads MCP servers, accounts for their tools in the model context window, and enters compaction. Reproduce the 94k/128k-tools scenario if possible; done means the CLI detects that MCP content exceeds the available context and warns the user before continuous compaction begins.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.