chi step of keccakf for small field

[Soleimani193]

This PR implements the chi step of keccakf for migration to the small field.

Checklist

• I wrote new tests for my new core changes.
• I have successfully ran tests, style checker and build against my new changes locally.
• I have informed the team of any breaking changes if there are any.

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Note

Implements the chi step for small-field keccakf (KoalaBear), exports the RC pattern helper, refactors the linear-combination sub-protocol, and adds targeted tests.

• ZK-EVM Keccakf (KoalaBear):
  • Chi step: new chi module building 8-bit linear combinations, applying chi logic, adding RC via RepeatedPattern, and producing witness (stateNextWitness).
  • Tests: chi_test validates reconstruction of the state post Chi+Iota over multiple permutations.
• Sub-protocols:
  • LinearCombination: rename to exported LinearCombination, new ctor NewLinearCombination, compute via keccakf.BaseRecompose, and add DecomposeForTesting; add protocols_test.
• Keccakf Lookups:
  • Export ValRCBase2Pattern and update usages/tests.
• Dedicated Protocol:
  • Add TestRepeatedPatWithVerifCol using verifiercol.NewConstantCol with RepeatedPattern.

^{Written by Cursor Bugbot for commit 60b855d. This will update automatically on new commits. Configure here.}

[cursor]

Bug: Round Constant Addition Loop Error

The symbolic definition for the round constant addition in newChi repeatedly adds the constant to StateNext[0][0][0] due to a hardcoded z index within a loop. This multiple addition creates an inconsistency with the assignChi function, which correctly applies the constant once, causing proof verification to fail.