Consolidate preserved open PR value onto main

[christopherkarani]

Summary

• preserves TraceKit and OTLP hardening from Mission-critical audit remediation: OTLP, TraceKit, and OpenTelemetry edge-case hardening #12
• preserves HTTP AI request/response parser hardening from Harden OpenTelemetry install flow #4
• reconciles overlapping telemetry and runtime audit value from Refine Terra telemetry install locking and runtime handling #3, Harden OpenTelemetry install for metrics and runtime overrides #5, Harden Terra telemetry defaults and error privacy handling #6, Align OpenTelemetry setup defaults and runtime install fixes #8, Fix OpenTelemetry defaults and runtime install behavior #9, and Fix Terra OpenTelemetry defaults and locking #10 into one coherent implementation on main
• selectively salvages still-relevant TraceKit invalid filename and discovery behavior from Enforce terra.v1 contract with policy gating and TraceMacApp controls #11
• notes that Add TerraTraceKit product to TraceMacApp #2 and Update TraceMacApp build metadata and docs #7 were already effectively contained on main and were not replayed wholesale

Intentionally skipped

• stale TraceMacApp-only changes
• stale app, UI, artifact, and bookkeeping churn that no longer matches the current repo layout
• nil-clearing runtime override behavior that regressed full-suite span capture

Verification

• swift build
• swift test