fix: use correct param keys for add and delete column ops

[alikhere]

Description

The right-click context menu for adding and deleting columns was silently broken for every user. Both handleAddColumn and handleDeleteColumn in Table.jsx were sending the request body with the key col_params, but the backend TransformationInput schema expects add_col_params and del_col_params respectively. FastAPI would set those fields to None and the handler would throw a 400. This fixes the fix is two key renames: col_params → add_col_params in handleAddColumn and col_params → del_col_params in handleDeleteColumn.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

How Has This Been Tested?

Ran npm run test (48 frontend tests pass), npm run lint, and npm run build — all clean. Ran uv run pytest on the backend — 92 tests pass. The one pre-existing failure (test_add_column_without_name_returns_422) was confirmed to exist on main before this branch and is tracked separately as issue #4. Manually verified that right-clicking a column header and choosing "Add Column" and "Delete Column" now succeeds instead of showing the error toast.

• Existing tests pass
• New tests added
• Manual testing

Fixes #257

Screenshots (if applicable)

After fix:

dataloom2.mp4

Checklist

• My code follows the project's style guidelines
• I have performed a self-review
• I have added/updated documentation as needed
• My changes generate no new warnings
• Tests pass locally

[alikhere]

Hi @ivantha , Could you please review the PR whenever you get time.
Thanks!