5b7e0223aa
Carries #268 onto #258's new head, which now sits on #247's re-merge
(12f206fb) and so on #239's spanned_values and &Expansion signatures.
Code auto-merged: GridLayout::evaluator / GridEval stays the only public
path to a FoldMemo, and prune_empty still shares one memo. The one
conflict was benches/grid_projection.rs's main(): both new sections kept,
the pruned block kept directly after the folded chain it calls "the same".
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze