fix(aztec-nr): tolerate malformed partial-note completion logs (#24668)

## Problem

Partial-note discovery has four crash points on the completion path,
each reachable by a malicious sender and each firing before the pending
note advances — so every subsequent sync re-hits it and permanently
freezes note sync for that contract:

- a matched completion log yields no note (`panic`),
- a pending note resolves to more than one completion log (`assert`),
- the delivered private half plus the log's public content exceed the
packed-note capacity (`BoundedVec` overflow in the append), or
- the completion log payload is empty, so reading the storage slot is
out of bounds.

The first three are reachable on the canonical token (mismatched content
over the unconstrained delivery channel, completing the same partial
note twice which the token does not prevent, and an over-length
delivered private half); the last needs an attacker-controlled contract
emitting a tag-only log.

## Fix

Make each non-fatal: warn and advance the FSM rather than panicking, so
one bad message cannot break sync. A completion log that cannot yield a
note (empty, over-length, or matching none) is skipped; more than one
completion log completes with the first.

Fixes F-798

Author: nchamo

noir-projects/aztec-nr/aztec/src/messages/processing/log_retrieval_response.nr

@@ -1,5 +1,8 @@
 use crate::messages::logs::note::MAX_NOTE_PACKED_LEN;
-use crate::protocol::{constants::{MAX_NOTE_HASHES_PER_TX, PRIVATE_LOG_CIPHERTEXT_LEN}, traits::Deserialize};
+use crate::protocol::{
+    constants::{MAX_NOTE_HASHES_PER_TX, PRIVATE_LOG_CIPHERTEXT_LEN},
+    traits::{Deserialize, Serialize},
+};
 
 pub global MAX_PUBLIC_LOG_LEN_FOR_NOTE_COMPLETION: u32 = MAX_NOTE_PACKED_LEN;
 
@@ -11,7 +14,7 @@ pub(crate) global MAX_LOG_CONTENT_LEN: u32 = std::cmp::max(
 /// A response to a `LogRetrievalRequest`, containing the payload of a log (i.e. the content minus the tag, called
 /// plaintext for public logs and ciphertext for private), plus contextual information about the transaction in which
 /// the log was emitted. This is the data required in order to discover notes that are being delivered in a log.
-#[derive(Deserialize, Eq)]
+#[derive(Deserialize, Eq, Serialize)]
 pub struct LogRetrievalResponse {
     pub log_payload: BoundedVec<Field, MAX_LOG_CONTENT_LEN>,
     pub tx_hash: Field,

noir-projects/aztec-nr/aztec/src/messages/processing/mod.nr

@@ -95,6 +95,13 @@ pub unconstrained fn enqueue_note_for_validation(
     ))
 }
 
+/// The note validation requests enqueued so far in the current context via [`enqueue_note_for_validation`], before
+/// [`validate_and_store_enqueued_notes_and_events`] drains them. Exists so tests can inspect the pending queue;
+/// production code should not read requests back once enqueued.
+pub(crate) unconstrained fn get_enqueued_note_validation_requests() -> EphemeralArray<NoteValidationRequest> {
+    EphemeralArray::at(NOTE_VALIDATION_REQUESTS_ARRAY_BASE_SLOT)
+}
+
 /// Enqueues an event for validation and storage by PXE.
 ///
 /// This is the primary way for custom message handlers (registered via