fix: anvil process hangs when exiting

[holic]

this PR force-kills (with SIGKILL) the anvil process after the stopTimeout elapses

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PR-Codex overview

This PR enhances the createAnvil.ts file in Anvil.js by adding a conditional check to gracefully stop the Anvil process and kill it forcefully if needed.

Detailed summary

• Added a conditional check to gracefully stop and kill the Anvil process if necessary.

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Latest commit: cd96aee

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