Add daemon-backed OpenCode npm plugin - #7

Summary

• import @braintrust/trace-opencode as monorepo-owned npm package content while preserving its four Braintrust data-access tools
• delete the standalone JavaScript tracing processor, API sink, queue, replay, git metadata, file logger, and their tracing-only tests
• keep OpenCode tracing as a thin fail-open adapter that forwards native events to the daemon and performs no span construction or Braintrust API delivery
• delegate all four data-access tools to non-interactive bt CLI commands; the npm package contains no Braintrust HTTP client, API-key handling, or credential management
• forward optional profile/org/project selection to both the daemon and tool CLI invocations; bt owns default-profile resolution, keychain/OAuth access, refresh, and backend routing
• add the private reusable newline-delimited JSON-RPC client; shared daemon delivery stamps braintrust.plugin.<source> using the package version supplied by each JavaScript adapter
• add the OpenCode Rust translator, npm tarball build/validation/publish-safety scripts, compatibility CI, and actual-agent integration coverage

Validation

• make test
• make validate-opencode
• bun test src/runtime/js-daemon-client/tests
• cargo test --manifest-path bt-daemon/Cargo.toml --all-features --locked
• cargo clippy --manifest-path bt-daemon/Cargo.toml --all-targets --all-features --locked -- -D warnings
• BT_AGENT_INFERENCE_MODE=mock BT_AGENT_INGEST_MODE=mock cargo test --manifest-path bt-daemon/Cargo.toml --all-features --locked --test agent_integration opencode_session_emits_traces -- --ignored --nocapture --test-threads=1 using OpenCode 1.18.13 locally
• tool delegation unit coverage for SQL, project listing/creation, experiment listing, and temporary bt sync push input cleanup
• isolated tarball imports with the claimed OpenCode peer range in CI

The real-agent scenario installs the built npm tarball, loads it in the actual OpenCode CLI, calls deterministic mock inference, forwards native events over JSON-RPC, and verifies daemon-produced rows at mock Braintrust ingest. It also verifies shared OpenCode origin name and package version metadata.

Release safety

No npm package, marketplace repository, tag, or GitHub release was published. Real npm publishing requires an explicit release confirmation.

Merge dependency

This remains draft until the companion bt embedding implements AuthProvider through its existing non-interactive profile resolver. The profile is optional and resolves to the default automatically when omitted.