docs(ecosystem): add opencode-langsmith-tracing plugin

[Dramalf]

Issue for this PR

Closes #20168

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds the plugin opencode-langsmith-tracing to the Plugins table.

It streams the OpenCode session — conversation turns, individual LLM calls (including the continuation step after a tool call), tool invocations, reasoning blocks, token / cost accounting, and context compaction — into a LangSmith project as a single nested trace. The shape mirrors langsmith-claude-code-plugins on purpose, so people who already have LangSmith dashboards or evaluators built for Claude Code don't have to redo them.

• npm: https://www.npmjs.com/package/opencode-langsmith-tracing
• repo: https://github.com/Dramalf/opencode-langsmith-tracing
• license: MIT

How did you verify your code works?

Been running it locally on OpenCode 1.4.11 for the past few days against a LangSmith deployment. Things I specifically checked:

• Single-turn replies (a plain "hi") show up as one Turn → one Assistant LLM run.
• Tool-using turns (e.g. asking for a directory listing → model calls bash ls → continues with a written answer) come through as Turn → Assistant step 1 → bash tool → Assistant step 2, with the second step's text and tokens captured.
• Token usage, cost, and reasoning blocks land on the right runs.
• Interrupting a turn mid-response closes the trace as error: "Interrupted" instead of leaving it open.

For this PR specifically: it's a single line in a markdown table. I previewed the rendered docs locally (bun dev in packages/web) to make sure the table still parses.

Screenshots / recordings

A screenshot from Langsmith tracing page

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[Dramalf]

The work is done and tested