chore: fix accumulation logic for PrimeField vectors

[mdqst]

updated the accumulation from using .sum() to an explicit .fold(F::zero(), |acc, x| acc + x).
this ensures correct behavior for all F: PrimeField types and resolves the issue with summing field elements.

[srinathsetty]

Can you say more on what the issue with using sum is?

[mdqst]

srinathsetty, sum() can be a bit tricky with field types - it goes through the Sum trait, which doesn’t always behave as expected for PrimeField elements (especially with refs and generic bounds). Using an explicit fold(F::zero(), |acc, x| acc + x) makes the accumulation unambiguous and guarantees it stays within the field operations. just safer and clearer

[Copilot]

Pull Request Overview

This PR fixes the accumulation logic for PrimeField vectors by replacing .sum() with an explicit .fold(F::zero(), |acc, x| acc + x) operation. This change ensures correct behavior when summing field elements in the sparse matrix-vector multiplication implementation.

Key Changes:

• Updated the accumulation method in SparseMatrix::multiply to use explicit folding instead of .sum()

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[mdqst]

srinathsetty, lets merge it

[srinathsetty]

srinathsetty, lets merge it

Can we please fix CI failures?

[mdqst]

srinathsetty done

[mdqst]

srinathsetty lets merge it