Symmetrize STRIDE Δ matrices#191

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d-burg wants to merge 7 commits intodevelopfrom

Commits on Jan 23, 2025

WIP: deltaprime symmetrization outline
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Commits on Jan 28, 2025

WIP: STRIDE sym dependency updates
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Commits on Jan 31, 2025

WIP: broken, but integral progress
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Commits on Feb 4, 2025

WIP: looks roughly correct but yields wrong answers
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Commits on Feb 17, 2025

WIP: check original delta matrices for symmetry
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Commits on Jun 24, 2025

merging with develop
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Commits on Jun 26, 2025

new splining and correct integral(J)
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