feat(otel): add HTTP/protobuf transport support alongside gRPC

[kmkinney]

Add OPENCODE_OTLP_PROTOCOL env var to select between gRPC (default) and HTTP/protobuf OTLP exporters. The default endpoint port adjusts automatically (4317 for gRPC, 4318 for HTTP) when OPENCODE_OTLP_ENDPOINT is not set. Accepts 'grpc', 'http/protobuf', or 'http' as shorthand.

Description

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Chore (dependency updates, etc.)

Checklist

• I have read the CONTRIBUTING.md document
• My code follows the style guidelines of this project
• bun run typecheck passes with no errors
• bun test passes with no errors
• I have added tests that prove my fix is effective or that my feature works
• I have updated the documentation accordingly
• My commits follow the Conventional Commits specification

Related issues

Additional context