(CODUX-216) Implement bounded Foreach fan-out

[numnx]

🧩 Task: Implement bounded Foreach fan-out

Automated task PR opened by Code UX for T20.

📋 Summary

Sprint: Sprint 216 · Nodes Full Integration · Task: T20

Turn the existing project-scoped node-flow foundation and browser-local canvas into a canonical, secure, versioned automation control plane with registry-driven nodes, encrypted credentials, durable execution, governed integrations, isolated custom nodes, agent authoring, dashboard integration, and authenticated headless readiness.

🤖 Model & Provider

Provider	Codex CLI
Model	gpt-5.6-sol

⏱️ Timing

Started	2026-07-12 09:27:47 UTC
Finished	2026-07-12 09:41:30 UTC
Duration	13m 42s

📊 Token Usage

Metric	Value
Input tokens	199,833
Cached input tokens	6,485,248
Output tokens	27,609
Total tokens	6,712,690
Invocations	1
Tool calls	66
Active time	13m 17s

Included usage estimate (subscription/local login): $5.07

✅ QA Review

⏳ QA review runs after this PR is opened. Check the task card in the dashboard for the outcome once it lands.

📝 Full Task Prompt

### Objective
Make the Foreach built-in perform bounded per-item downstream execution with durable logical-item tracking.

### Requirements
Extend runtime scheduling so Foreach emits bounded logical items, downstream nodes execute once per item with configured concurrency limits, item-specific inputs and attempts are persisted, empty branches are explicitly skipped, cancellation and retry semantics remain durable, and side-effect idempotency keys include the logical item. Reject inputs above the configured bound.

### Verification
Add tests for zero, one, and many items, concurrency bounds, item failures, retries, cancellation, approval-gated sends, restart recovery, and duplicate-side-effect prevention. Run built-in/runtime/recovery tests, backend tests, typecheck, and build.

🌿 Branch Info

Base: feature/CODUX-216-nodes-full-integration
Head: task/feature-codux-21-t20-codex-887de861-mrhlbjt9

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🤖 Generated by Code UX