docs(cipher-factory): document public API types

Add doc comments to OutputFormat, OperationMode enums and their methods.
Add crate-level documentation describing the factory's purpose.

aes/src/operations/column_mix.rs

@@ -1,6 +1,6 @@
 use crate::Block128;
 
-/// Mixes each column using matrix multiplication in GF(2^8) (MixColumns step).
+/// Mixes each column using matrix multiplication in GF(2^8) ([`MixColumns`] step).
 ///
 /// Each column is treated as a polynomial and multiplied by a fixed polynomial
 /// modulo x^4 + 1. This provides diffusion across the rows.

aes/src/operations/round_key.rs

@@ -1,6 +1,6 @@
 use crate::{Block128, key::Subkey};
 
-/// XORs the state with a round key (AddRoundKey step).
+/// XORs the state with a round key ([`AddRoundKey`] step).
 ///
 /// Each round of AES combines the current state with a derived subkey
 /// using bitwise XOR. This operation is its own inverse.

aes/src/operations/row_shift.rs

@@ -1,6 +1,6 @@
 use crate::Block128;
 
-/// Cyclically shifts rows of the state matrix (ShiftRows step).
+/// Cyclically shifts rows of the state matrix ([`ShiftRows`] step).
 ///
 /// Row 0: no shift, Row 1: shift left 1, Row 2: shift left 2, Row 3: shift left 3.
 /// This provides diffusion across the columns.

aes/src/operations/sbox_lookup.rs

@@ -1,6 +1,6 @@
 use crate::{Block128, sbox::SboxLookup};
 
-/// Substitutes each byte using the AES S-box (SubBytes step).
+/// Substitutes each byte using the AES S-box ([`SubBytes`] step).
 ///
 /// Provides non-linearity by replacing each byte with its S-box lookup value.
 /// The S-box is derived from the multiplicative inverse in GF(2^8).