Fix converter output display

[Creylay]

Summary

Two related fixes to the session preprocessing wizard: two converter steps of the same type used to render with an identical name (e.g. two "Simple Imputer" cards), which made them hard to tell apart, and when scoping a new converter over an earlier step's output group, the picker showed the raw internal key (e.g. __group__0) instead of a readable label.

---

Type of Change

Check all that apply like this [x]:

• Backend change
• Frontend change
• CI / Workflow change
• Build / Packaging change
• Bug fix
• Documentation

---

Changes (by file)

• sessionColumnRefs.js: added buildStepDisplayNames, which numbers steps that share a converter type by order of appearance (e.g. "Simple Imputer", "Simple Imputer (2)"), and threaded an optional convertersMeta through buildColumnKeysAndTypes so its option labels use these disambiguated names.
• AppliedConvertersView.jsx: replaced its own local name-resolution logic with the shared buildStepDisplayNames, and dropped the redundant "(slot)" text from an output group's label now that its type is already shown as a colored chip next to
• SelectColumnsStep.jsx: now fetches converter metadata and passes it into buildColumnKeysAndTypes, so the final column-selection step shows the same disambiguated names as the rest of the wizard.
• ColumnSelector.jsx (shared with Notebooks): added an optional optionLabels prop. A row whose key has a label (a converter's output group) now renders as a chip with its
  name and a colored type badge, matching the same chip style used elsewhere.l renders as plain text, unchanged.
• ScopeStepSessionConverter.jsx: now passes the resolved optionLabels (previously discarded) into ColumnSelector, fixing the raw __group__0 key showing up when scoping a
  new converter over an earlier step's output.
• FormSessionConverterSection.jsx, SessionConvertersRightBar.jsx: threaded convertersMeta (already fetched in the right bar for the converter list) down to
  ScopeStepSessionConverter, so its labels match the disambiguated names us
• sessionColumnRefs.test.js, AppliedConvertersView.test.jsx: added coverage for the numbering behavior and the removal of the redundant slot text.

---

Testing (optional)

• Manually verified in the wizard: adding two Simple Imputer steps shows "Simple Imputer" and "Simple Imputer (2)" consistently in the applied converters view and in the final column selection step, and scoping a new converter over a previous step's output group now shows a proper labeled chip instead of a raw __group__0 key.