Replaces the bespoke batch-scoped process.exit interceptor with the
withExitGuard convention main established for extension/hook/plugin
loaders (500c39aa2): guard the module import and factory invocation so
a synchronous process.exit()/process.reallyExit() from a custom tool
becomes an ExtensionExitError handled as a recoverable load error,
while host exit paths stay untouched outside the guarded windows.
Tests cover the import-time exit (issue #1704 repro) and factory-time
exit; both would kill the test process without the guard.
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