chore: Add clarfiication on the difference in recursive aggregation c…

…ircuits (#4567)

# Description

## Problem\*

Resolves comment here
#4563 (comment)

## Summary\*



## Additional Context



## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[Exceptional Case]** Documentation to be submitted in a separate
PR.

# PR Checklist\*

- [ ] I have tested the changes locally.
- [ ] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

test_programs/execution_success/double_verify_nested_proof/src/main.nr

@@ -1,10 +1,18 @@
 use dep::std;
 
+// This circuit aggregates two recursive proofs from `double_verify_proof_recursive`.
+// Recursive aggregation is a backend-specific process and it is expected for backends 
+// to attach any extra data they may need (e.g. aggregation objects) to their proofs. 
+// Whether the proof we are verifying itself contains a recursive proof is expected to be 
+// a circuit constant by the barretenberg. Barretenberg hides this circuit constant in the 
+// proof serialization. Thus, we must have separate circuits for verifying a normal proof and a recursive proof
+// with two different proof sizes.
 fn main(
     verification_key: [Field; 114],
-    // This is the proof without public inputs attached.
-    // 
-    // This means: the size of this does not change with the number of public inputs.
+    // This is the proof without user-specified public inputs attached.
+    //
+    // This means: the size of this does not change with the number of public inputs unless
+    // they have been attached by the backend.
     proof: [Field; 109],
     public_inputs: pub [Field; 1],
     // This is currently not public. It is fine given that the vk is a part of the circuit definition.

test_programs/execution_success/double_verify_proof/src/main.nr

@@ -1,5 +1,6 @@
 use dep::std;
 
+// This circuit aggregates two proofs from `assert_statement_recursive`.
 fn main(
     verification_key: [Field; 114],
     // This is the proof without public inputs attached.

test_programs/execution_success/double_verify_proof_recursive/src/main.nr

@@ -1,5 +1,6 @@
 use dep::std;
 
+// This circuit aggregates two proofs from `assert_statement_recursive`.
 #[recursive]
 fn main(
     verification_key: [Field; 114],