fix(telemetry): bump semconv to v1.39 to match OTel SDK 1.40 schema URL

[zulkhair]

Summary

Fixes a runtime panic introduced when PR #894's OTel SDK bump (v1.38 → v1.40) made resource.Default() use schema URL v1.39.0 while pkg/telemetry/setup.go still imported semconv/v1.37.0. resource.Merge errors on conflicting schema URLs, so every cardinal shard panics on boot:

panic: failed to initialize telemetry: failed to setup telemetry:
  conflicting Schema URL: https://opentelemetry.io/schemas/1.39.0
                      and https://opentelemetry.io/schemas/1.37.0

Caught locally while testing the rampage-backend bump in Argus-Labs/rampage-backend#612 — every gameplay shard panicked at startup with the trace above.

Change

One-line import bump: semconv/v1.37.0 → semconv/v1.39.0. v1.39 is what OTel SDK 1.40's resource.Default() reports as its schema URL, so the merge succeeds.

The semconv subpackage ships inside go.opentelemetry.io/otel itself (already at v1.40.0 in go.mod), so no dependency churn.

Test plan

• Built a rampage gameplay shard against this branch in the local _testing/ workspace — boots cleanly through telemetry init
• Confirmed shard's OTel exporter still publishes spans to the operator's OTLP receiver after the bump
• CI lint + tests

[zulkhair]

• fix(telemetry): bump semconv to v1.39 to match OTel SDK 1.40 schema URL #898 👈 (View in Graphite)
• main

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