When a Fit to Artwork Bounds step of `command.batch` takes the batch's
`artboard` as its `index`, the batch's journal entry now records that
`index`. Before, the entry kept the step without it, so a replay with the
Artboard tool choosing two or more artboards fitted those instead.
The params text, docs/mcp.md and docs/target-app-parity.md state that the
step uses the Artboard tool's selection only when two or more artboards
are selected, and the active artboard otherwise.