Harden Terra telemetry defaults and error privacy handling

[christopherkarani]

Summary

• add telemetry-specific privacy keys and default OTLP endpoints plus rollback safety
• ensure inference timing uses uptime and error events honor privacy/redaction settings
• add regression tests for OpenTelemetry rollback and error privacy 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Superseded by #15, which consolidates the still-valid changes from the current open PR set onto main and intentionally skips stale or conflicting churn.