fix(blockchain): adapt the heartbeat tier to main's rejection taxonomy

Main replaced `InvalidValidatorIndex` with index-specific variants, made
`is_slot_justified` fallible, added a genesis field this branch also
extends, and made `rejection_reason` exhaustive so a new `StoreError`
forces a classification decision.

The heartbeat variants report as unclassified for now: leanSpec names no
rejection reason for the tier yet, so a placeholder mapping would assert
a reason no fixture agrees with. Revisit when the spec covers heartbeat
vote validation.

The two projection-window assertions read an untracked slot as "not
justified yet", matching how the packer's pre-filter treats its own
window.

Author: MegaRedHand

bin/ethlambda/src/main.rs

@@ -773,6 +773,7 @@ async fn fetch_initial_state(
 mod tests {
     use super::*;
     use ethlambda_storage::backend::InMemoryBackend;
+    use ethlambda_types::constants::DEFAULT_HEARTBEAT_COMMITTEE_SIZE;
     use ethlambda_types::genesis::GenesisValidatorEntry;
 
     /// Validator-config snippet matching `lean-quickstart`'s ansible-devnet
@@ -898,6 +899,7 @@ validators:
     fn test_genesis(genesis_time: u64) -> GenesisConfig {
         GenesisConfig {
             genesis_time,
+            heartbeat_committee_size: DEFAULT_HEARTBEAT_COMMITTEE_SIZE,
             genesis_validators: vec![GenesisValidatorEntry {
                 attestation_pubkey: [1u8; 52],
                 proposal_pubkey: [2u8; 52],

crates/blockchain/src/block_builder.rs

@@ -1325,7 +1325,10 @@ mod tests {
                 &advanced.justified_slots,
                 advanced.finalized_slot,
                 data.target.slot,
-            ),
+            )
+            // Same reading as the packer's pre-filter: a slot the projection
+            // window does not track is not justified yet.
+            .unwrap_or(false),
             "a heartbeat entry must not justify its target on tier alone"
         );
 
@@ -1334,11 +1337,14 @@ mod tests {
         // `advance` being inert.
         let mut justified = empty_projection();
         justified.advance(EntryEffect::Justifies, &data, HashSet::from([7]));
-        assert!(justified_slots_ops::is_slot_justified(
-            &justified.justified_slots,
-            justified.finalized_slot,
-            data.target.slot,
-        ));
+        assert!(
+            justified_slots_ops::is_slot_justified(
+                &justified.justified_slots,
+                justified.finalized_slot,
+                data.target.slot,
+            )
+            .unwrap_or(false)
+        );
     }
 
     /// Under cap pressure the surviving heartbeat entries must be the

crates/blockchain/src/spec_test_runner.rs

@@ -98,6 +98,12 @@ pub fn rejection_reason(err: &StoreError) -> Option<RejectionReason> {
         | StoreError::SignatureAggregationFailed(_)
         | StoreError::MissingTargetState(_)
         | StoreError::SlotOutOfRange(_) => return None,
+
+        // Placeholder: leanSpec names no rejection reason for the heartbeat tier
+        // yet, so these report as unclassified until it does. Revisit once the
+        // spec fixtures cover heartbeat vote validation.
+        StoreError::HeartbeatVoteOutOfSlot { .. }
+        | StoreError::NotHeartbeatCommitteeMember { .. } => return None,
     };
     Some(reason)
 }

crates/blockchain/src/store.rs

@@ -710,7 +710,10 @@ pub fn on_gossip_heartbeat_attestation(
         .ok_or(StoreError::MissingTargetState(data.target.root))?;
     let num_validators = target_state.validators.len() as u64;
     if validator_id >= num_validators {
-        return Err(StoreError::InvalidValidatorIndex);
+        return Err(StoreError::AttesterIndexOutOfRange {
+            validator_index: validator_id,
+            num_validators,
+        });
     }
 
     if !is_heartbeat_committee_member(