Add HITL API router to expose review data to the UI

[selvicim45]

Title: Add HITL API router to expose review data and accept human decisions

Description

We currently create HITL review jobs in HITLNode (e.g., review_id, customer, safe variants, status). However, there is no dedicated API surface for the UI to:

• Fetch details for a given review (customer + variants + status)
• Submit a human reviewer decision (which variant is approved, optional notes)

This issue is to implement a simple HITL router in the backend so the front end can integrate with the human-in-the-loop flow.

Scope

Use the existing store (e.g., MemoryStore) where HITLNode saves reviews under keys like hitl:{review_id}.

Expose endpoints to:

• Get HITL review payload by review_id
• Submit human decision for review_id (approved variant, notes)

Proposed implementation

Extend HITLNode (if not already)

Ensure HITLNode.run(customer, safe_variants) saves the following structure in the store:

{
  "customer": {...},
  "variants": [...],
  "status": "pending_human_approval"
}

Uses key pattern:

hitl:{review_id}

---

Create new router: backend/app/routers/hitl.py

GET /hitl/{review_id}

• Loads store.get(f"hitl:{review_id}")
• Returns { customer, variants, status, ... }
• Returns 404 if review is not found

POST /hitl/{review_id}/decision

Request body (Pydantic model):

{
  "approved_variant_id": "A",
  "notes": "optional free text"
}

Backend logic:

• Load hitl:{review_id}
• Update:
  • status = "approved"
  • approved_variant_id
  • notes
• Save updated object back to store

---

Register router in app/main.py

Add:

from .routers.hitl import router as hitl_router
app.include_router(hitl_router)

---

Acceptance Criteria

GET /hitl/{review_id} returns:

• customer
• variants
• status

POST /hitl/{review_id}/decision:

• Updates review with:
  • status="approved"
  • approved_variant_id
  • notes

Additional Criteria

• Both endpoints visible and testable in Swagger (/docs)
• End-to-end flow works:

Trigger orchestration
→ HITLNode creates review
→ review is fetchable via GET /hitl/{review_id}
→ decision is submitted via POST /hitl/{review_id}/decision