Expand description
The trace/telemetry spine, instrumented from Phase 1 (DESIGN.md §9).
An EventObserver is a passive consumer of the event stream — it never
writes to the world. This is the seam the reusable evaluation kernel
grows along: trace capture, scenario replay, and scoring all subscribe
here. SeasonTelemetry is the first concrete consumer, and doubles as the
embryo of the Phase-2 calibration harness (goals/game, home advantage —
the exact aggregates the harness will check against reality).