Implement OpenAI Agents span processing

[nagkumar91]

Description

Updates the previous barebones PR to include genai spans and traces.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Testing

• Manual agents example: cd instrumentation-genai/opentelemetry-instrumentation-openai-agents/examples/manual && cp .env.example .env (populate OPENAI_API_KEY, optional OTLP vars) then python3 main.py; confirmed travel response prints and spans export
  cleanly with integer timestamps.
• Zero-code example: cd instrumentation-genai/opentelemetry-instrumentation-openai-agents/examples/zero-code && cp .env.example .env (set API key) then python3 main.py; verified auto-configured instrumentation loads env defaults and completes without
  exporter errors.
• Unit tests: From repo root, with .venv active and pip install -e .[examples] applied, ran python3 -m pytest opentelemetry-instrumentation-openai-agents/tests/test_tracer.py; all tests passed, confirming span translation logic handles nanosecond
  timestamps and attribute mapping.

Environment

• Python 3.9.6 inside the project’s .venv.
• Dependencies installed via pip install -e instrumentation-genai/opentelemetry-instrumentation-openai-agents[examples].
• OTLP collector optional; when unavailable, spans export successfully to the default console exporter.

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated