refactor: add verbose logging to OrphanBlockManager expiry and add

Log orphan additions (hash, prev, map size) and expirations (hash, age,
count expired, remaining) at VERBOSE level for observability during
forking events.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jamescowens

src/node/orphan_blocks.cpp

@@ -36,6 +36,9 @@ bool OrphanBlockManager::Add(const uint256& hash, const CBlock& block, int64_t n
     m_orphans.emplace(hash, std::move(entry));
     m_by_prev.emplace(prev_hash, hash);
 
+    LogPrint(BCLog::LogFlags::VERBOSE, "OrphanBlockManager: added orphan %s (prev=%s, map size %u)",
+             hash.ToString(), prev_hash.ToString(), m_orphans.size());
+
     return true;
 }
 
@@ -108,6 +111,10 @@ size_t OrphanBlockManager::EraseExpired(int64_t now)
     for (auto it = m_orphans.begin(); it != m_orphans.end(); ) {
         if (now - it->second.time_received > MAX_ORPHAN_AGE_SECONDS) {
             const uint256 hash = it->first;
+            const int64_t age = now - it->second.time_received;
+
+            LogPrint(BCLog::LogFlags::VERBOSE, "OrphanBlockManager: expiring orphan %s (age %" PRId64 "s, map size %u)",
+                     hash.ToString(), age, m_orphans.size());
 
             // Clean up SeenStakes before erasing.
             if (it->second.block->IsProofOfStake()) {
@@ -123,6 +130,11 @@ size_t OrphanBlockManager::EraseExpired(int64_t now)
         }
     }
 
+    if (count > 0) {
+        LogPrint(BCLog::LogFlags::VERBOSE, "OrphanBlockManager: expired %u orphans, %u remaining",
+                 count, m_orphans.size());
+    }
+
     return count;
 }