dgb: pin oracle SOFTFORKS_REQUIRED set (DGB-distinctive reservealgo+odo) (#273)

Test-only Phase-B pool/share conformance guard. Locks PoolConfig::
SOFTFORKS_REQUIRED to the oracle set in frstrtr/p2pool-dgb-scrypt
networks/digibyte.py:25 — {nversionbips,csv,segwit,reservealgo,odo,
taproot}. reservealgo and odo are DigiByte-unique; a silent add or
drop would mis-signal softfork requirements vs the oracle network.

Fenced to src/impl/dgb/test/share_test.cpp only; no shared-base,
CMake, or build.yml touch; dgb_share_test already allowlisted. No
consensus value changes (guards what already ships). 10/10 green.

Co-authored-by: frstrtr <frstrtr@users.noreply.github.com>

Author: frstrtr

src/impl/dgb/test/share_test.cpp

@@ -22,6 +22,8 @@
 #include <impl/dgb/coin/rpc_conf.hpp>   // #82 external-daemon RPC creds (digibyte.conf)
 
 #include <cstdio>
+#include <set>
+#include <string>
 #include <fstream>
 
 // Sharechain-identity: the isolation primitives (PREFIX / IDENTIFIER) are the
@@ -66,6 +68,23 @@ TEST(DGB_share_test, OraclePoolShareLayer)
               "00000fffffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
 }
 
+// SOFTFORKS_REQUIRED — DGB-distinctive softfork-signalling set. reservealgo
+// and odo are DigiByte-unique (absent from BTC/LTC); a silent drop here makes
+// the embedded daemon mis-signal softfork requirements vs the oracle network.
+// Oracle SSOT: frstrtr/p2pool-dgb-scrypt networks/digibyte.py:25
+//   set([nversionbips,csv,segwit,reservealgo,odo,taproot])
+TEST(DGB_share_test, OracleSoftforksRequired)
+{
+    const std::set<std::string> kExpected = {
+        "nversionbips", "csv", "segwit", "reservealgo", "odo", "taproot"
+    };
+    EXPECT_EQ(dgb::PoolConfig::SOFTFORKS_REQUIRED, kExpected);
+    // Loud guard on the DGB-unique members + cardinality (catches add OR drop).
+    EXPECT_EQ(dgb::PoolConfig::SOFTFORKS_REQUIRED.count("reservealgo"), 1u);
+    EXPECT_EQ(dgb::PoolConfig::SOFTFORKS_REQUIRED.count("odo"),         1u);
+    EXPECT_EQ(dgb::PoolConfig::SOFTFORKS_REQUIRED.size(),               6u);
+}
+
 // v35 donation = forrestv P2PK (4104ffd0…ac, 65-byte pubkey push + CHECKSIG).
 // v36 donation = combined P2SH (23-byte). get_donation_script() switches on
 // share_version at the SEGWIT/merged boundary.