command `yaak import --workspace-id` creates duplicates instead of updating existing items

Re-importing items that already exist in the workspace (same IDs) creates new copies with new IDs instead of updating them.

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Steps:

1. yaak export file.json wk_xyz
2. Edit a websocket_request in file.json (e.g. change folderId), keep its id
3. yaak import file.json –workspace-id wk_xyz

Expected: existing request updated (the bundled agent skill says “Workspace and request IDs survive an export/import”)

Actual: a second request and folder with new IDs; originals are unchanged