Function: createInterceptorContext()
createInterceptorContext(
env):InterceptorRuntime
Build an InterceptorContext + its InterceptorRuntime.
Teardown is the generalized superviseExit: the first child exit or main-process
termination signal flips a one-shot guard, SIGTERMs the other bound children,
then process.exits after TEARDOWN_GRACE_MS (an unref’d timer, so it
never itself holds the loop open). The process-signal listeners are installed
lazily on the first bindProcess so an app that binds nothing is untouched.