Fix test linker errors: extern scope in Boost.Test namespace

Move extern declarations to file scope so they resolve to global
symbols instead of the Boost test suite namespace. Cast static const
member to avoid ODR address requirement.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/test/consensus_tests.cpp

@@ -6,6 +6,10 @@
 #include "../main.h"
 #include "../kernel.h"
 
+// These globals are defined in main.cpp but not declared in any header
+extern unsigned int nTargetSpacing;
+extern unsigned int nStakeMaxAge;
+
 BOOST_AUTO_TEST_SUITE(consensus_tests)
 
 // --- Chain constants that must never change ---
@@ -75,20 +79,16 @@ BOOST_AUTO_TEST_CASE(pow_cutoff)
 BOOST_AUTO_TEST_CASE(timing_constants)
 {
     // 2-minute block target
-    extern unsigned int nTargetSpacing;
-    BOOST_CHECK_EQUAL(nTargetSpacing, 120u);
+    BOOST_CHECK_EQUAL(::nTargetSpacing, 120u);
 
     // 1-hour minimum stake age
-    extern unsigned int nStakeMinAge;
-    BOOST_CHECK_EQUAL(nStakeMinAge, 3600u);
+    BOOST_CHECK_EQUAL(::nStakeMinAge, 3600u);
 
     // 12-hour maximum stake age (pre-V5 fork)
-    extern unsigned int nStakeMaxAge;
-    BOOST_CHECK_EQUAL(nStakeMaxAge, 43200u);
+    BOOST_CHECK_EQUAL(::nStakeMaxAge, 43200u);
 
     // Modifier interval
-    extern unsigned int nModifierInterval;
-    BOOST_CHECK_EQUAL(nModifierInterval, 300u);  // 5 minutes
+    BOOST_CHECK_EQUAL(::nModifierInterval, 300u);  // 5 minutes
 }
 
 BOOST_AUTO_TEST_CASE(coinbase_maturity)

src/test/serialization_tests.cpp

@@ -146,7 +146,7 @@ BOOST_AUTO_TEST_CASE(block_header_roundtrip)
 
 BOOST_AUTO_TEST_CASE(block_current_version)
 {
-    BOOST_CHECK_EQUAL(CBlock::CURRENT_VERSION, 6);
+    BOOST_CHECK_EQUAL((int)CBlock::CURRENT_VERSION, 6);
 }
 
 // --- CDiskTxPos ---