Since 0.5.0 — the hook is registered and never invoked:
createCausl() throws where it used to degrade, so there is no fallback to
report. Kept exported for one release so a listener written against 0.4.x
still compiles; removed in 0.6.0. Catch the construction error and branch
on its code instead.
Register the process-wide TS-fallback telemetry hook. Returns an unsubscribe that restores the prior hook.