Session-scoped autouse fixture in tests/ttp/conftest.py sets
DECNET_DEVELOPER_TRACING=true and forces decnet.telemetry._ENABLED
so the no-op tracer doesn't silently swallow emitted spans. The
span_exporter fixture also monkeypatches decnet.telemetry.get_tracer
so production code under test lands spans in the in-memory
exporter. Tracing tests skip when DECNET_OTEL_ENDPOINT (default
localhost:4317) isn't reachable so the dev loop stays green
without lying about coverage.
In-memory span exporter fixture wired to a per-test TracerProvider
(OTEL global is locked once set, so each test gets its own).
ttp.eval / ttp.lifter.{name} / ttp.rule.fire / ttp.rule.state.change
hierarchy + no-PII canary battery xfail-gated behind E.3.5–E.3.13.
