Oddly my env was borked bc a missing sub-dep (`typing-extensions`
apparently not added by `uv` for `stackscope`?) and then `stackscope`
was silently failing import and caused the shield-pause test to also
fail (since it couldn't match the expected `log.devx()` on console). The
import failure is not very explanatory due to the `log.warning()`;
change it to `.error()` level.
Also, explicitly import `_sync_pause_from_builtin` in
`examples/debugging/restore_builtin_breakpoint.py` to ensure the ref is
exported properly from `.devx.debug` (which it wasn't during dev of the
prior commit Bp).
c2e7dc7407