Duplicate a v3 dashboard

Copy an existing v3 dashboard: a new engine=v3 row over the SAME dataset, the source's draft canvas copied verbatim (titled 'Copy of <title>') with its baked bundle carried onto the copy so it opens without a re-bake. Synchronous — there is no LLM and no re-resolution (the dataset is identical, so the source bake stays valid), so a job + poll would only add latency. Gated on the dashboards-v3 workspace flag (a create flow, like /v3/generate) plus editor on the SOURCE dashboard.

With target_dataview_id the copy is created in THAT view's project (the caller needs read on the view and create in the project) and the data-swap job is enqueued to re-point it — swap_job_id is the job to poll. Columns that match keep the author's choices. Without it, behaviour is unchanged.