Refine Terra telemetry install locking and runtime handling

[christopherkarani]

Summary

• simplify Terra.installOpenTelemetry locking flow, ensure persistence/metrics are configured without double-unlock, and clear meters when metrics are disabled
• streamline Runtime.install overrides and metrics wiring plus make recordInference use computed values safely
• switch inference span timing to ContinuousClock and add coverage for runtime install cleanup and concurrent install failure handling

Testing

• Not run (not requested)

[christopherkarani]

Superseded by #15, which consolidates the still-valid changes from the current open PR set onto main and intentionally skips stale or conflicting churn.