Remove temporary files after interrupted atomic saves

[OskarEichler]

Summary

Delete the temporary file when an atomic save raises Interrupt or another Exception outside StandardError, while preserving the original failure and store contents.

Reproduction and verification

Injected IOError and Interrupt during temporary-file writes. Both must propagate, leave the old store value intact and remove temporary files. Existing code leaves a temporary file behind for Interrupt.

• External focused corpus: 6 verified on this isolated branch under rbenv Ruby 4.0.6.
• Existing upstream RBENV_VERSION=4.0.6 rbenv exec rake test: 13 tests / 26 assertions, zero failures before and after.
• All files and injected failures are confined to scratch storage; no production operations.
• No repository tests added or modified under the contributor's task constraint. Other Ruby versions and native Windows were not executed locally.

Breaking-change notes and limitations

No normal-output or format change. Cleanup is attempted before propagating the exception. No guarantee is made for process termination, power loss or arbitrary asynchronous termination at every instruction.