[Feature Request]: Create Sub-Pipeline/Mapping from a selected set of transforms

### What would you like to happen?

In Apache Hop, when multiple transforms are selected inside a Pipeline, the user should be able to right-click the selection (or any selected transform) and see a new context-menu action: “Create Sub-Pipeline” or “Create Mapping”.
When triggered, the system encapsulates the selected transforms into a new artifact and replaces the selection with a single step referencing that new artifact.

Key functional requirements:

Visible only when 2+ transforms are selected.

Create a new sub-pipeline/mapping containing the selected transforms and internal hops.

Auto-rewire external inputs/outputs to the new reference step.

Preserve transform configuration and metadata.

Provide a minimal dialog for:

artifact name,

save location,

“open created artifact” option.

Acceptance criteria:

After “Create Sub-Pipeline/Mapping”, the editor replaces the selection with one reference step.

External connections remain valid and runtime behavior is unchanged.

For multiple entry/exit points, the UI provides consistent ports or clear validation guidance.

Rationale (why this matters):

Speed: eliminates repetitive manual extraction work.

Consistency: promotes modular design and reuse.

Maintainability: keeps main pipelines readable and easier to evolve.

Reliability: automated rewiring reduces configuration mistakes.

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui

Start in the Hop Gui pipeline editor, focusing on transform selection and the context-menu action described in the issue. Trace how selected transforms, internal hops, external connections, and artifact dialogs are handled. Done means creating a sub-pipeline or mapping from at least two selected transforms, preserving configuration, rewiring connections, and replacing the selection with one reference step.

Written by the indexing model from the issue text.