[Feature Request]: Metadata Injection keeps obsolete mappings after changing the source or template pipeline

### What would you like to happen?

When using ETL Metadata Injection, if the source pipeline or template pipeline is modified or replaced, existing metadata injection mappings are not automatically cleaned up.

As a result, mappings can continue referencing transforms that no longer exist in the selected pipelines. This leads to errors such as:

Source transform 'METADADOS JSON' is not available in 'raw_etl_metadata' pipeline!
Target transform 'JSON DADOS' is not defined in 'raw_template' pipeline!
Target transform 'SEL. FORMATACAO' is not defined in 'raw_template' pipeline!

Apache Hop is able to detect these invalid mappings and displays the “Invalid mapping” dialog asking whether the missing mappings should be removed. However, the obsolete mappings should ideally be cleared or revalidated automatically when the source/template pipeline changes, preventing invalid references from remaining in the configuration.

### Issue Priority

Priority: 3

### Issue Component

Component: Transforms

Start with the ETL Metadata Injection transform and reproduce the problem by changing or replacing its source and template pipelines. Trace how existing mappings are retained and verify that obsolete references are cleared or revalidated automatically, with no invalid-mapping errors remaining.

Written by the indexing model from the issue text.