Create: Human Input node configuration — default/custom action handles, persistence (§3.9)

[daniellicnerski1]

Wave 5 — 1.11.0 feature coverage.

Backlog pointer: QA-CHECKLIST.md §3.9 → core-components/human-input-node-config.spec.ts

Scope

• Human Input node renders default Approve/Reject branch handles.
• Adding a custom User Action (action-add-input) creates a new handle live.
• Configured handles persist after save + page reload.

Upstream: langflow-ai/langflow#13633 / LE-1449. Manual recipe: QA platform item HITL-01.