docs: add documentation for FriE2F4 operation

[VolodymyrBg]

Description:
Add comprehensive documentation for the FriE2F4 operation in the core operations module. The documentation includes:

• Description of FRI layer folding operation
• List of operations performed
• Detailed stack transition diagram with input and output states
• Explanation of stack overflow table interaction

This documentation helps developers better understand the FRI protocol implementation in the Miden VM and improves code maintainability.

[plafer]

Left a few nits.

Could you also rebase this on top of the latest next branch?

[VolodymyrBg]

@plafer Done

[plafer]

@VolodymyrBg I just noticed that Operation variants do in fact have big docstrings - apologies for misleading you.

I don't recall exactly what you had initially, but basically something along the lines of this should work (even copy/paste).

[VolodymyrBg]

@plafer
/// Performs FRI (Fast Reed-Solomon Interactive Oracle Proofs) layer folding by a factor of 4
/// for FRI protocol executed in a degree 2 extension of the base field.
///
/// This operation:
/// - Folds 4 query values (v0, v1), (v2, v3), (v4, v5), (v6, v7) into a single value (ne0, ne1)
/// - Computes new value of the domain generator power: poe' = poe^4
/// - Increments layer pointer (cptr) by 2
/// - Checks that the previous folding was done correctly
/// - Shifts the stack to move an item from the overflow table to stack position 15
///
/// Stack transition:
/// Input: [v7, v6, v5, v4, v3, v2, v1, v0, f_pos, d_seg, poe, pe1, pe0, a1, a0, cptr, ...]
/// Output: [t1, t0, s1, s0, df3, df2, df1, df0, poe^2, f_tau, cptr+2, poe^4, f_pos, ne1, ne0, eptr, ...]
/// where eptr is moved from the stack overflow table and is the address of the final FRI layer.

[plafer]

Yes that works

[VolodymyrBg]

@plafer should i correct the file again?