Add otlp-env-vars skill for OpenTelemetry SDK env var configuration

[Copilot]

This PR adds a dedicated skill for OpenTelemetry SDK environment-variable configuration so agents can apply spec-aligned behavior when configuring or debugging OTLP-related setups. It captures the canonical parsing/validation rules and consolidates the highest-signal variables/operators into one reusable reference.

• Scope

  • Adds a new skill file: .github/skills/otlp-env-vars/SKILL.md
  • Introduces a focused guide for env-var-driven SDK configuration and troubleshooting

• Spec-critical behavior captured

  • Empty value == unset
  • Boolean semantics (true case-insensitive only)
  • Invalid numeric handling (warn + ignore)
  • Enum handling (case-insensitive; unknown values warn + ignore)

• Configuration coverage

  • General SDK vars (OTEL_SDK_DISABLED, OTEL_SERVICE_NAME, OTEL_RESOURCE_ATTRIBUTES, etc.)
  • Exporter selection across traces/metrics/logs
  • BSP/BLRP batch processor knobs and defaults
  • Limits + metrics controls
  • OTEL_CONFIG_FILE precedence behavior over flat SDK env vars

• Operational guidance

  • Adds a compact troubleshooting checklist ordered around highest-impact failure modes (config-file override, empty values, booleans/enums, per-signal exporter split, implementation support)

---
name: otlp-env-vars
description: Configure and troubleshoot OpenTelemetry SDK environment variables safely.
---