kernel: Move BlockInfo to a kernel file

diff --git a/ci/test/03_test_script.sh b/ci/test/03_test_script.sh
index 7f8fad71..d29de80c 100755
--- a/ci/test/03_test_script.sh
+++ b/ci/test/03_test_script.sh
@@ -209,7 +209,7 @@ if [ "${RUN_TIDY}" = "true" ]; then
   fi
 
   # TODO: Consider enforcing IWYU across the entire codebase.
-  FILES_WITH_ENFORCED_IWYU="/src/((crypto|index)/.*\\.cpp|node/blockstorage.cpp|node/utxo_snapshot.cpp|core_read.cpp|signet.cpp)"
+  FILES_WITH_ENFORCED_IWYU="/src/((crypto|index)/.*\\.cpp|node/blockstorage.cpp|node/utxo_snapshot.cpp|core_read.cpp|signet.cpp|kernel/chain.cpp)"
   jq --arg patterns "$FILES_WITH_ENFORCED_IWYU" 'map(select(.file | test($patterns)))' "${BASE_BUILD_DIR}/compile_commands.json" > "${BASE_BUILD_DIR}/compile_commands_iwyu_errors.json"
   jq --arg patterns "$FILES_WITH_ENFORCED_IWYU" 'map(select(.file | test($patterns) | not))' "${BASE_BUILD_DIR}/compile_commands.json" > "${BASE_BUILD_DIR}/compile_commands_iwyu_warnings.json"
 
diff --git a/src/index/base.cpp b/src/index/base.cpp
index 425f9f7e..7f77d13a 100644
--- a/src/index/base.cpp
+++ b/src/index/base.cpp
@@ -9,7 +9,6 @@
 #include <dbwrapper.h>
 #include <interfaces/chain.h>
 #include <interfaces/types.h>
-#include <kernel/chain.h>
 #include <kernel/types.h>
 #include <logging.h>
 #include <node/abort.h>
diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 686da67b..e6847b9b 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -7,6 +7,7 @@
 
 #include <blockfilter.h>
 #include <common/settings.h>
+#include <kernel/chain.h> // IWYU pragma: export
 #include <node/types.h>
 #include <primitives/transaction.h>
 #include <util/result.h>
@@ -78,22 +79,6 @@ public:
     mutable bool found = false;
 };
 
-//! Block data sent with blockConnected, blockDisconnected notifications.
-struct BlockInfo {
-    const uint256& hash;
-    const uint256* prev_hash = nullptr;
-    int height = -1;
-    int file_number = -1;
-    unsigned data_pos = 0;
-    const CBlock* data = nullptr;
-    const CBlockUndo* undo_data = nullptr;
-    // The maximum time in the chain up to and including this block.
-    // A timestamp that can only move forward.
-    unsigned int chain_time_max{0};
-
-    BlockInfo(const uint256& hash LIFETIMEBOUND) : hash(hash) {}
-};
-
 //! The action to be taken after updating a settings value.
 //! WRITE indicates that the updated value must be written to disk,
 //! while SKIP_WRITE indicates that the change will be kept in memory-only
diff --git a/src/kernel/chain.cpp b/src/kernel/chain.cpp
index da515a05..0a33e9a1 100644
--- a/src/kernel/chain.cpp
+++ b/src/kernel/chain.cpp
@@ -2,9 +2,10 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <chain.h>
-#include <interfaces/chain.h>
 #include <kernel/chain.h>
+
+#include <chain.h>
+#include <kernel/cs_main.h>
 #include <kernel/types.h>
 #include <sync.h>
 #include <uint256.h>
diff --git a/src/kernel/chain.h b/src/kernel/chain.h
index 9675bb0f..5afa51f4 100644
--- a/src/kernel/chain.h
+++ b/src/kernel/chain.h
@@ -5,12 +5,31 @@
 #ifndef BITCOIN_KERNEL_CHAIN_H
 #define BITCOIN_KERNEL_CHAIN_H
 
-#include<iostream>
+#include <attributes.h>
+
+#include <iostream>
 
 class CBlock;
 class CBlockIndex;
+class CBlockUndo;
+class uint256;
+
 namespace interfaces {
-struct BlockInfo;
+//! Block data sent with blockConnected, blockDisconnected notifications.
+struct BlockInfo {
+    const uint256& hash;
+    const uint256* prev_hash = nullptr;
+    int height = -1;
+    int file_number = -1;
+    unsigned data_pos = 0;
+    const CBlock* data = nullptr;
+    const CBlockUndo* undo_data = nullptr;
+    // The maximum time in the chain up to and including this block.
+    // A timestamp that can only move forward.
+    unsigned int chain_time_max{0};
+
+    BlockInfo(const uint256& hash LIFETIMEBOUND) : hash(hash) {}
+};
 } // namespace interfaces
 
 namespace kernel {