refactor: graceful exit batch stop

[samuv]

as per title a little refactor using the batch api endpoint instead of calling stop on each server when we do the graceful exit

[Copilot]

Pull request overview

Refactors the app’s graceful-exit shutdown flow to stop running servers via the ToolHive bulk stop endpoint (batch API) instead of issuing per-server stop requests, and updates the existing Vitest coverage accordingly.

Changes:

• Switch stopAllServers to call postApiV1BetaWorkloadsStop once with a names list.
• Remove per-server stop fan-out (Promise.allSettled) and associated aggregated failure reporting.
• Update graceful-exit tests to validate the new batch-stop request shape and error behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
main/src/graceful-exit.ts	Replaces per-server stop calls with a single bulk stop request and reuses the same polling-to-final-state flow.
main/src/tests/graceful-exit.test.ts	Updates mocks/expectations to assert a single bulk stop call (body.names) and aligns failure expectations with the new behavior.