copilot-cli does not persist environment variables between tool calls.

### Describe the bug

Working with beads mcp server there are many issues, these all seem to resolve to a difference between copilot-cli and many other codeing clis.

see the following issue report for an explaination.

https://github.com/steveyegge/beads/issues/246

### Affected version

0.0.354

### Steps to reproduce the behavior

use the list function in the beads-mcp server

### Expected behavior

environment variable set on an mcp tool call, is not persisted to the next call.

### Additional context

_No response_