[4.5] Atom property maps with the view toggle

[CSSFrancis]

Ellipticity, nearest-neighbour distance, monolayer spacing, displacement from the ideal lattice.

Shipped through the same commit_result_tree view mechanism as [1.8] so the maps toggle like strain components.

Part of #74.

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Plan: RELEASE_0_3_0_PLAN.md

[CSSFrancis]

Delivered in 0.3.0, merged to main via #89.

56d04b1 — feat(atoms): atom finding, GPU refinement, property maps

Closing from the merge rather than automatically: the commits cite issues as (#79) rather than Closes #79, so GitHub linked none of them (#89 reported 0 closing references).