## Context

When the dev container creation modal is showing "Creating Dev
Container", clicking anywhere on the workspace backdrop dismisses the
dialog. The container creation continues in the background, but the user
loses visual feedback and the subsequent `open_remote_project` call may
fail because the modal entity is gone.

This adds an `allow_dismissal` flag to `RemoteServerProjects` that
blocks accidental dismissal (backdrop clicks, focus loss) while a dev
container is being created, but allows explicit dismissal on success or
error.

## How to Review

Small PR — two files changed:

1. **`remote_servers.rs`** (the fix): `allow_dismissal` bool field
added, set to `false` when entering Creating state, set to `true` before
emitting `DismissEvent` on success/error. `on_before_dismiss` override
checks the flag.
2. **`recent_projects.rs`** (the test): Regression test that opens a dev
container modal, simulates a backdrop click, and asserts the modal stays
open.

## 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 is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- Fixed dev container creation modal being dismissed when clicking
outside it

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>