Align GLOAS fork choice with spec

- Move proposer boost from apply_score_changes to get_weight, matching
  the spec's structure where get_weight adds boost via is_supporting_vote
- Implement is_supporting_vote and get_ancestor_node spec functions
- Fix should_extend_payload: return true when proposer_boost_root is zero
- Compute record_block_timeliness from time_into_slot instead of hardcoding false
- Fix anchor block_timeliness to [true, true] per get_forkchoice_store spec
- Add equivocating_attestation_score for is_head_weak monotonicity
- Use payload-aware weight in is_parent_strong
- Add with_status helper on IndexedForkChoiceNode
- Simplify find_head_walk to return IndexedForkChoiceNode directly

consensus/fork_choice/src/fork_choice.rs

@@ -797,6 +797,11 @@ where
         let attestation_threshold = spec.get_unaggregated_attestation_due();
 
         // Add proposer score boost if the block is timely.
+        // TODO(gloas): the spec's `update_proposer_boost_root` additionally checks that
+        // `block.proposer_index == get_beacon_proposer_index(head_state)` — i.e. that
+        // the block's proposer matches the expected proposer on the canonical chain.
+        // This requires calling `get_head` and advancing the head state to the current
+        // slot, which is expensive. Implement once we have a cached proposer index.
         let is_before_attesting_interval = block_delay < attestation_threshold;
 
         let is_first_block = self.fc_store.proposer_boost_root().is_zero();
@@ -1001,6 +1006,7 @@ where
             self.justified_checkpoint(),
             self.finalized_checkpoint(),
             spec,
+            block_delay,
         )?;
 
         Ok(())