Cleanup and spec parity fixes

- Add missing payload attestation slot check: spec returns early when
  data.slot != block.slot (PTC votes only for assigned block)
- Remove dead ignored tests (need mock EL Gloas support to run)
- Remove unused new_with_gloas and inspect_queued_payload_attestations
- Remove gloas entries from bin.rs (not part of this PR)
- Collapse nested if in payload attestation error handling (clippy)
- Rename env -> envelope in load_parent
- Add TODO(gloas) for parent_head_hash in re-org path
- Remove head_payload_status from ForkchoiceUpdateParameters (lives on
  CachedHead, sourced from get_head return)

consensus/fork_choice/src/fork_choice.rs

@@ -1216,6 +1216,12 @@ where
             });
         }
 
+        // Spec: `if data.slot != state.slot: return` — PTC votes can only
+        // change the vote for their assigned beacon block.
+        if block.slot != indexed_payload_attestation.data.slot {
+            return Ok(());
+        }
+
         // Gossip payload attestations must be for the current slot.
         // https://github.com/ethereum/consensus-specs/blob/master/specs/gloas/fork-choice.md
         if matches!(is_from_block, AttestationFromBlock::False)