chore: add initial Claude.md (#3252)

Author: galkleinman

CLAUDE.md

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+# OpenLLMetry Repository Guide
+
+## Repository Structure
+This repository contains multiple PyPI-publishable packages organized and orchestrated using Nx workspace management.
+
+### Nx Workspace Commands
+```bash
+# Run tests across all packages
+nx run-many -t test
+
+# Run linting across all packages
+nx run-many -t lint
+
+# Update lock files across all packages
+nx run-many -t lock
+
+# Run specific targets on specific packages
+nx run <package-name>:test
+nx run <package-name>:lint
+
+# Show project graph
+nx graph
+
+# Show what's affected by changes
+nx affected:test
+nx affected:lint
+```
+
+## Package Management
+All packages use Poetry as the package manager. Always execute commands through Poetry:
+```bash
+poetry run <command>
+```
+
+## Testing with VCR Cassettes
+Tests utilize VCR cassettes for API calls.
+
+### Commands
+```bash
+# Run tests normally (uses existing cassettes)
+poetry run pytest tests/
+
+# Re-record all cassettes (requires API keys)
+poetry run pytest tests/ --record-mode=all
+
+# Record only new test episodes
+poetry run pytest tests/ --record-mode=new_episodes
+
+# Record cassettes once (if they don't exist)
+poetry run pytest tests/ --record-mode=once
+
+# Run tests without recording (fails if cassettes missing)
+poetry run pytest tests/ --record-mode=none
+
+# Run specific test files
+poetry run pytest tests/test_agents.py --record-mode=once
+```
+
+### Guidance
+Re-record cassettes when API interactions change to ensure test accuracy.
+Never commit secrets or PII. Scrub them using VCR filters (e.g., filter_headers, before_record) or your test framework's equivalent.
+Store API keys only in environment variables/secure vaults; never in code or cassettes.
+Typical record modes you may use: once, new_episodes, all, none (choose per test needs).
+Creating new cassettes requires valid API keys (OpenAI, Anthropic, etc.); ask the user to provide them if needed.
+
+## Semantic Conventions
+The semantic convention package follows the OpenTelemetry GenAI specification:
+https://opentelemetry.io/docs/specs/semconv/gen-ai/
+
+## Instrumentation Packages
+Instrumentation packages should leverage the semantic conventions package. Their purpose is to instrument AI-related libraries and generate spans and tracing data compliant with OpenTelemetry semantic conventions.
+
+## Code Quality
+Flake8 is used for code linting.