Feat/opentelemetry instrumentation

[Ray0907]

• Add OpenTelemetry instrumentation that bridges aiEventClient events to
  OTEL spans

  • Follow GenAI Semantic Conventions (gen_ai.system, gen_ai.usage.*, etc.)
  • Create spans for chat, stream, tool calls, and iterations
  • Support configurable content recording for privacy
  • Remove console.log/error from openai and anthropic adapters (security
    improvement)

  🎯 Changes

  Add @tanstack/ai-opentelemetry package that automatically creates
  OpenTelemetry traces and spans for all TanStack AI operations by
  subscribing to the existing aiEventClient event system.

  New Package: @tanstack/ai-opentelemetry

  • Bridges aiEventClient events to OTEL spans
  • Follows GenAI Semantic Conventions
  • Creates spans for: chat, stream, tool calls, iterations
  • Configurable content recording (disabled by default for privacy)

  Security Improvement

  • Remove console.log/error from @tanstack/ai-openai and
    @tanstack/ai-anthropic adapters
  • Errors are still properly emitted via StreamChunk error type

  ✅ Checklist

  • I have followed the steps in the Contributing
    guide.
  • I have tested this code locally with pnpm run test:pr.

  🚀 Release Impact

  • This change affects published code, and I have generated a
    [changeset](https://github.com/changesets/changesets/blob/main/docs/adding
    -a-changeset.md).
  • This change is docs/CI/dev-only (no release).