dgb(phase-b): extract PPLNS payout-split SSOT (weights -> consensus-sorted payout outputs)

Lift steps 2-3 of share_check.hpp generate_share_transaction (PPLNS amount
math + consensus output ordering) into a pure, tracker-free helper
coin/pplns_payout_split.hpp: compute_pplns_payout_split(). This is the bridge
that lets the per-connection Stratum coinbase assembler draw the SAME payout
amount split the share verification SSOT enforces, so emission and verification
cannot diverge on a satoshi.

Additive/fenced: nothing calls it yet (no behavior change). Follow-ons:
(1) delegate generate_share_transaction to it (byte-identity), (2) wire it into
DGBWorkSource::build_connection_coinbase feeding ConnCoinbaseInputs.payout_outputs.

KAT dgb_pplns_payout_split_test: V36 exact amounts + >=1 sat donation floor,
pre-V36 amounts + 0.5%% finder fee, empty-weights bootstrap, zero-amount drop;
all against hand-computed p2pool v36 data.py oracle vectors. Registered in the
test CMakeLists and both build.yml dgb --target allowlists (#143 NOT_BUILT trap).

Author: frstrtr

.github/workflows/build.yml

@@ -81,7 +81,7 @@ jobs:
                     test_mweb_builder \
                     test_address_resolution test_compute_share_target \
                     test_utxo test_dgb_subsidy test_dgb_coinbase_value dgb_share_test dgb_redistribute_test dgb_block_assembly_test dgb_header_sample_build_test dgb_header_ingest_test dgb_mempool_ingest_test \
-                    dgb_gentx_coinbase_test dgb_connection_coinbase_test nmc_auxpow_merkle_test nmc_template_builder_test nmc_auxpow_wire_test nmc_reconstruct_won_block_test dgb_gentx_share_path_test dgb_other_tx_resolver_test \
+                    dgb_gentx_coinbase_test dgb_connection_coinbase_test dgb_pplns_payout_split_test nmc_auxpow_merkle_test nmc_template_builder_test nmc_auxpow_wire_test nmc_reconstruct_won_block_test dgb_gentx_share_path_test dgb_other_tx_resolver_test \
                     dgb_other_tx_assembler_test dgb_reconstruct_won_block_test dgb_reconstruct_closure_test dgb_gentx_unpack_test dgb_work_source_test dgb_template_builder_test dgb_embedded_coin_node_test dgb_embedded_tx_select_test dgb_template_other_txs_test dgb_coinbase_value_parity_test dgb_submit_classify_test dgb_aux_parent_coinbase_parity_test dgb_template_capture_test dgb_aux_doge_db_commitment_bind_test \
                     rpc_request_test softfork_check_test genesis_check_test algo_select_test digishield_walk_test header_chain_test \
                     dgb_coin_node_seam_test dgb_block_broadcast_test dgb_won_block_dispatch_test dgb_forced_won_share_dualpath_test dgb_scrypt_pow_test dgb_nonce_grinder_test dgb_regrind_block_test dgb_won_block_finalize_test v37_test \
@@ -213,7 +213,7 @@ jobs:
                     test_mweb_builder \
                     test_address_resolution test_compute_share_target \
                     test_utxo test_dgb_subsidy test_dgb_coinbase_value dgb_share_test dgb_redistribute_test dgb_block_assembly_test dgb_header_sample_build_test dgb_header_ingest_test dgb_mempool_ingest_test \
-                    dgb_gentx_coinbase_test dgb_connection_coinbase_test nmc_auxpow_merkle_test nmc_template_builder_test nmc_auxpow_wire_test nmc_reconstruct_won_block_test dgb_gentx_share_path_test dgb_other_tx_resolver_test \
+                    dgb_gentx_coinbase_test dgb_connection_coinbase_test dgb_pplns_payout_split_test nmc_auxpow_merkle_test nmc_template_builder_test nmc_auxpow_wire_test nmc_reconstruct_won_block_test dgb_gentx_share_path_test dgb_other_tx_resolver_test \
                     dgb_other_tx_assembler_test dgb_reconstruct_won_block_test dgb_reconstruct_closure_test dgb_gentx_unpack_test dgb_work_source_test dgb_template_builder_test dgb_embedded_coin_node_test dgb_embedded_tx_select_test dgb_template_other_txs_test dgb_coinbase_value_parity_test dgb_submit_classify_test dgb_aux_parent_coinbase_parity_test dgb_template_capture_test dgb_aux_doge_db_commitment_bind_test \
                     rpc_request_test softfork_check_test genesis_check_test algo_select_test digishield_walk_test header_chain_test \
                     dgb_coin_node_seam_test dgb_block_broadcast_test dgb_won_block_dispatch_test dgb_forced_won_share_dualpath_test dgb_scrypt_pow_test dgb_nonce_grinder_test dgb_regrind_block_test dgb_won_block_finalize_test test_coin_broadcaster test_multiaddress_pplns test_pplns_stress \

src/impl/dgb/coin/pplns_payout_split.hpp

@@ -0,0 +1,138 @@
+#pragma once
+// ============================================================================
+// pplns_payout_split.hpp — SSOT: PPLNS weights -> consensus-sorted payout outputs.
+//
+// Converts the decayed/cumulative PPLNS weight map (produced by the ShareTracker
+// — see share_tracker.hpp get_v36_decayed_cumulative_weights /
+// get_cumulative_weights) into the EXACT integer per-script payout amounts and
+// the consensus output ordering that the coinbase carries.
+//
+// This is steps 2-3 of share_check.hpp generate_share_transaction() lifted into
+// a pure, tracker-free, chain-free function so the SAME math can feed BOTH:
+//   - generate_share_transaction()        (the share verification SSOT), and
+//   - stratum/work_source build_connection_coinbase() (per-connection coinbase),
+// guaranteeing emission and verification can never diverge on a payout satoshi.
+//
+// Port of frstrtr/p2pool-merged-v36 data.py generate_transaction() amount math:
+//   V36:     amounts[script] = subsidy * weight / total_weight
+//   Pre-V36: amounts[script] = subsidy * (199 * weight) / (200 * total_weight)
+//            amounts[finder] += subsidy // 200          (0.5% finder fee)
+//   donation = subsidy - sum(amounts)
+//   V36 floor: donation must carry >= 1 sat (a60f7f7f) — deduct 1 from the
+//              largest payout, deterministic tiebreak (amount, script).
+//   order:   sorted(dests, key=(amount, script))[-4000:]  (asc, keep highest)
+//
+// Pure: takes already-built weights + subsidy + finder script, so it is directly
+// KAT-able against a canonical oracle vector (test/pplns_payout_split_test.cpp).
+// ============================================================================
+
+#include <core/uint256.hpp>   // uint288
+
+#include <algorithm>
+#include <cstdint>
+#include <map>
+#include <utility>
+#include <vector>
+
+namespace dgb::coin
+{
+
+// Maximum coinbase payout outputs, matching p2pool's [-4000:] slice.
+inline constexpr std::size_t PPLNS_MAX_OUTPUTS = 4000;
+
+struct PplnsPayoutSplit
+{
+    // (scriptPubKey, value) pairs in final consensus order: ascending by
+    // (amount, script), truncated to the highest PPLNS_MAX_OUTPUTS.
+    std::vector<std::pair<std::vector<unsigned char>, uint64_t>> payout_outputs;
+    // donation = subsidy - sum(payout amounts) (after the v36 >=1 sat floor).
+    uint64_t donation_amount{0};
+};
+
+// weights / total_weight: PPLNS weight map keyed by full scriptPubKey.
+// subsidy: total coinbase value to distribute (block subsidy + fees).
+// use_v36_pplns: select the V36 formula (no finder fee) vs pre-V36 (0.5% fee).
+// finder_script: share creator's payout script — receives the pre-V36 finder
+//                fee; ignored when use_v36_pplns is true.
+inline PplnsPayoutSplit compute_pplns_payout_split(
+    const std::map<std::vector<unsigned char>, uint288>& weights,
+    const uint288& total_weight,
+    uint64_t subsidy,
+    bool use_v36_pplns,
+    const std::vector<unsigned char>& finder_script)
+{
+    std::map<std::vector<unsigned char>, uint64_t> amounts;
+
+    // --- exact integer payout amounts (generate_share_transaction step 2) ---
+    if (!total_weight.IsNull())
+    {
+        for (auto& [script, weight] : weights)
+        {
+            uint64_t amount;
+            if (use_v36_pplns)
+            {
+                // V36: amounts[script] = subsidy * weight / total_weight
+                uint288 num = uint288(subsidy) * weight;
+                amount = (num / total_weight).GetLow64();
+            }
+            else
+            {
+                // Pre-V36: amounts[script] = subsidy * (199 * weight) / (200 * total_weight)
+                uint288 num = uint288(subsidy) * (weight * 199);
+                uint288 den = total_weight * 200;
+                amount = (num / den).GetLow64();
+            }
+            if (amount > 0)
+                amounts[script] = amount;
+        }
+    }
+
+    // Pre-V36: add 0.5% finder fee to share creator.
+    if (!use_v36_pplns)
+        amounts[finder_script] += subsidy / 200;
+
+    // Donation = subsidy minus the sum of all payout amounts.
+    uint64_t sum_amounts = 0;
+    for (auto& [s, a] : amounts)
+        sum_amounts += a;
+    uint64_t donation_amount = (subsidy > sum_amounts) ? (subsidy - sum_amounts) : 0;
+
+    // V36 consensus: donation output must carry >= 1 satoshi (a60f7f7f).
+    // Deduct 1 sat from the largest miner payout; deterministic tiebreak
+    // (amount, script) — largest script wins when amounts are equal.
+    if (use_v36_pplns)
+    {
+        if (donation_amount < 1 && subsidy > 0 && !amounts.empty())
+        {
+            auto largest = std::max_element(amounts.begin(), amounts.end(),
+                [](const auto& a, const auto& b) {
+                    if (a.second != b.second) return a.second < b.second;
+                    return a.first < b.first;
+                });
+            if (largest != amounts.end() && largest->second > 0)
+            {
+                largest->second -= 1;
+                sum_amounts -= 1;
+                donation_amount = subsidy - sum_amounts;
+            }
+        }
+    }
+
+    // --- consensus output order (generate_share_transaction step 3) ---------
+    // Python: sorted(dests, key=lambda a: (amounts[a], a))[-4000:]
+    //   = ascending by (amount, script), keep last PPLNS_MAX_OUTPUTS (highest).
+    PplnsPayoutSplit out;
+    out.donation_amount = donation_amount;
+    out.payout_outputs.assign(amounts.begin(), amounts.end());
+    std::sort(out.payout_outputs.begin(), out.payout_outputs.end(),
+        [](const auto& a, const auto& b) {
+            if (a.second != b.second) return a.second < b.second; // asc by amount
+            return a.first < b.first;                             // asc by script tiebreak
+        });
+    if (out.payout_outputs.size() > PPLNS_MAX_OUTPUTS)
+        out.payout_outputs.erase(out.payout_outputs.begin(),
+                                 out.payout_outputs.end() - PPLNS_MAX_OUTPUTS);
+    return out;
+}
+
+} // namespace dgb::coin

src/impl/dgb/test/CMakeLists.txt

@@ -161,6 +161,21 @@ if (BUILD_TESTING AND GTest_FOUND)
         dgb_coin pool sharechain)
     gtest_add_tests(dgb_connection_coinbase_test "" AUTO)
 
+    # --- Phase B: PPLNS weights -> consensus-sorted payout outputs KAT ------
+    # Pins coin/pplns_payout_split.hpp: compute_pplns_payout_split reproduces
+    # steps 2-3 of share_check.hpp generate_share_transaction (the verification
+    # SSOT) satoshi-for-satoshi -- the bridge that lets build_connection_coinbase
+    # draw the SAME PPLNS amount split the share check enforces. Header-only over
+    # uint288, registered with the proven dgb link set for parity with sibling
+    # coinbase KATs. MUST also be in the build.yml --target allowlist (#143 trap).
+    add_executable(dgb_pplns_payout_split_test pplns_payout_split_test.cpp)
+    target_link_libraries(dgb_pplns_payout_split_test PRIVATE
+        GTest::gtest_main GTest::gtest
+        core dgb
+        c2pool_payout c2pool_merged_mining c2pool_hashrate c2pool_storage
+        dgb_coin pool sharechain)
+    gtest_add_tests(dgb_pplns_payout_split_test "" AUTO)
+
     # --- #172 share-path gentx KAT (collapse consumption proof) ------------
     # Proves generate_share_transaction (the verification SSOT call site #172
     # rewired) EMITS assemble_gentx_coinbase framing for a real v36 share, via