docs(research): plan traceWorkflowSpans for authored instrumentation

[cmpadden]

Summary

Related to #1779. Investigates whether defineInstrumentation can gain a traceWorkflowSpans option and adds the research plan for it. No runtime change.

instrumentations: [] cannot suppress Workflow spans because they are created manually via trace.getTracer("workflow") in @workflow/core, @workflow/world-local, and @workflow/world-vercel. eve also cannot reuse the AgentTraceSpanProcessor trick the issue cites: an authored instrumentation.ts owns the provider and the span processors, so eve has no export-time seam. The plan proposes the one interposition point eve does have — after the authored setup returns, replace the delegate of the global ProxyTracerProvider with a wrapper that returns a no-op tracer for the workflow scope.

Two things to weigh before implementing, both covered in the document alongside the rejected alternatives: this would be the first place eve mutates a tracer provider it does not own, and in the Workflow SDK's default linked trace mode the run-origin span link lives on the span being suppressed.

Validation

• pnpm guard:invariants (covers research frontmatter)
• Mechanism verified with throwaway scripts against the workspace's @vercel/otel + @opentelemetry/api: the global delegate swap is visible across module copies, Workflow packages resolve their tracer lazily so the swap lands first, and the exported topology keeps its trace id and re-parents agent spans onto the nearest surviving ancestor with no dangling parents
• No tests, docs, or changeset: this PR adds a research/ document only

Checklist

• I linked an issue with prior discussion confirming this change is wanted
• I ran the relevant checks from CONTRIBUTING.md
• I added tests and documentation where relevant
• I added a changeset if this touches the published eve package
• DCO sign-off passes for every commit (git commit --signoff)

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Project	Deployment	Actions	Updated (UTC)
eve-docs	Ready	Preview	Aug 7, 2026 7:43pm
eve-docs-4759	Ready	Preview, v0	Aug 7, 2026 7:43pm