fix: generate a script for every goal in `grind?` when parameters split the goal

This PR fixes `grind?` failing with "proof contains unresolved internal metavariable" when a parameter fact has a type marked `[grind cases eager]`. Asserting such a fact splits the goal during initialization, and `grind?` only produced a script for the first goal. It now handles every goal, and the suggested script carries one `·` block per goal.

The `grind only [...]` suggestions are unchanged, since the non-interactive replay splits inside the `finish` action.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>