Summary

Closes #372 — the reported "small offsets" in rectangular-mesh source-reconstruction plots. The bilinear interpolation mapper places value (row r, col c) at node U_y=(n_y−r−1)/(n_y−3), U_x=(c−1)/(n_x−3) in unit CDF space (guard ring, row = n − i flip), while edges_transformed drew a uniform [0,1] partition — pcolormesh put flux up to ~1.5 mesh pixels from where the mapper scatters it (delta-function reproduction on the issue). Edges are now the node midpoints through the same CDF machinery (guard-safe max(n−3,1) denominator; border guard cells clamp to the data span). Both consumers inherit the fix: the pcolormesh plot path and rectangular_rotated's warped-centre reconstruction; spline + linear CDFs share the upstream convention.

Plot geometry only — the mapper is untouched; inversions/likelihoods are byte-identical. Only where flux is drawn moves.

API Changes

Changed behaviour: RectangularMeshGeometry.edges_transformed returns mapper-consistent node-midpoint edges (previously a uniform unit-space partition). Consumers that treated it as a uniform grid see shifted (now correct) cell boundaries; the 3×3 degenerate case is value-identical via CDF clamping. Docstring corrected (was a copy-paste about pixel neighbors).

Test Plan

• pytest test_autoarray/ -q — 877 passed (incl. new delta-centroid regression: pre-fix uniform edges miss by ~0.4 units ≈ 1.5 cells in y; existing test__edges_transformed and rotated-mesh ghost tests unchanged)

Validation checklist (--auto run)

• Effective level: supervised (bug cap binds over safe header)
• Plan + confirmed root cause: on the issue (fix: rectangular-mesh pcolormesh plots misaligned with mapper node convention #372), sign-off question answered in-conversation ("go --auto")
• Gate: tests 877 pass · smoke n/a at this stage (downstream visual check recommended post-merge: regenerate a rectangular-mesh subplot from autolens_workspace_developer's plotting_alignment set) · review CLEAN · Heart YELLOW ⊆ in-session ack
• Human: merge, amend, or reject — then log the outcome

🤖 Generated with Claude Code