project: Refresh MCP settings after worktree changes (#62026)

# Objective

Prevent MCP servers from remaining unavailable when a project is created
before its first worktree.

## Solution

Refresh effective MCP settings before maintaining servers after worktree
additions or removals.

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

---

Release Notes:

- Agent: Fixed MCP servers missing from new project threads after a
worktree opens.
b5764581d2Ben Kunkle committed on 8/3/2026, 8:33:31 PM· committed by GitHubparent41c0f28
2 files changedLine totals unavailable