feat(frontend): migrate evaluator run invocation

[mmabrouk]

Summary

• add workflow invoke helper for SimpleEvaluator execution
• switch evaluator playground DebugSection to call /preview/workflows/invoke
• update migration plan/status docs for PR2 run migration

Testing

• pnpm lint-fix (warns about in web/oss/src/components/Editor/plugins/code/nodes/Base64Node.tsx)

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Project	Deployment	Review	Updated (UTC)
agenta-documentation	Ready	Preview, Comment	Jan 28, 2026 0:13am

[mmabrouk]

Decisions & Tradeoffs

• Use /preview/workflows/invoke from the evaluator playground instead of the legacy /evaluators/{key}/run. This matches the new backend path and keeps run logic aligned with SimpleEvaluator.
• Fallback URI when evaluator not saved: if no config exists yet, build via . This keeps Run Evaluator working for unsaved drafts.
• **Send parameters in both and **. The backend accepts both; this keeps compatibility with how workflow service requests are handled today.
• Minimal response typing: only surface and since UI currently only needs evaluator outputs.

Alternatives considered

• Keep legacy run endpoint (): lower change risk but blocks full migration; would keep old adapter path around.
• Require saved evaluator config before run: strict but would break current UX; reduces ambiguity around URI.
• **Only pass **: cleaner request but might miss expectations in existing workflow data handlers.
• Expose trace_id/span_id and surface in UI: more debugging power but requires UI changes.

If you prefer a different tradeoff (e.g., require saved configs or drop ), I can adjust this PR.