bch(m5): link pool-node TUs into c2pool-bch executable

Register node.cpp and the BCHWorkSource/protocol dispatch TUs in the
c2pool-bch add_executable stanza so NodeImpl:: symbols resolve, closing
the --pool/--stratum link gap. Additive single-coin CMake stanza; no
shared-base or peer-coin build changes. share_tracker.hpp carries the
pool-node share-write integration.

Author: frstrtr

src/c2pool/CMakeLists.txt

@@ -238,6 +238,15 @@ add_executable(c2pool-bch
     ${CMAKE_SOURCE_DIR}/src/impl/bch/coin/p2p_node.cpp
     ${CMAKE_SOURCE_DIR}/src/impl/bch/coin/coin_node.cpp
     ${CMAKE_SOURCE_DIR}/src/impl/bch/coin/rpc.cpp
+    # M5 pool-node body TUs: NodeImpl out-of-line methods (node.cpp) + the two
+    # p2pool p2p protocol dispatchers (Legacy/Actual handle_message_* family) +
+    # the stratum work source. These define the previously-undefined NodeImpl::
+    # and protocol symbols so the --pool path LINKS. Per-coin isolation holds
+    # (src/impl/bch only); compiled directly into the target like the coin TUs.
+    ${CMAKE_SOURCE_DIR}/src/impl/bch/node.cpp
+    ${CMAKE_SOURCE_DIR}/src/impl/bch/protocol_actual.cpp
+    ${CMAKE_SOURCE_DIR}/src/impl/bch/protocol_legacy.cpp
+    ${CMAKE_SOURCE_DIR}/src/impl/bch/stratum/work_source.cpp
 )
 target_compile_definitions(c2pool-bch PRIVATE C2POOL_VERSION="${C2POOL_GIT_VERSION}")
 # --ibd RUN-LOOP slice (integrator 2026-06-18): the read-only headers-first IBD

src/impl/bch/coin/embedded_daemon.hpp

@@ -100,7 +100,7 @@ class EmbeddedDaemon {
     /// EmbeddedCoinNode::getwork() is the live in-process work source.
     void run() {
         m_chain.init();               // load genesis / fast-start checkpoint (network-free)
-        m_node.run();                 // init_rpc(): external BCHN-RPC fallback retained
+        m_node.run(/*embedded_primary=*/true); // init_rpc(): eager external GBT non-fatal (embedded-primary); RPC fallback retained
         assemble();                   // network-free seam + ABLA wiring (see below)
         wire_chain_ingest();          // new_headers --> HeaderChain (advances synced height)
         pin_cold_start_anchor();      // operator-APPROVED VM300 anchor (decisions@ 2026-06-18); floor-equivalent

src/impl/bch/coin/node.hpp

@@ -55,13 +55,30 @@ class Node : public bch::interfaces::Node
         m_p2p->connect(m_config->coin()->m_p2p.address);
     }
 
-    void init_rpc()
+    // embedded_primary: when the in-process embedded daemon is the PRIMARY work
+    // source (v36 external_fallback invariant), a dead / 0-peer external BCHN that
+    // cannot yet answer getblocktemplate must NOT abort bring-up -- the embedded
+    // source provides work and the external RPC is only the fallback sink. When the
+    // external RPC IS the work source (embedded_primary == false), a failure here
+    // stays fatal exactly as before.
+    void init_rpc(bool embedded_primary)
     {
         m_rpc = std::make_unique<NodeRPC>(m_context, this, m_config->m_testnet);
         m_rpc->connect(m_config->m_rpc.address, m_config->m_rpc.userpass);
 
-        // work
-        work.set(m_rpc->getwork());
+        // work (eager prime from external RPC)
+        if (embedded_primary) {
+            try {
+                work.set(m_rpc->getwork());
+            } catch (const std::exception& e) {
+                LOG_WARNING << "[EMB-BCH] init_rpc: external BCHN getwork() unavailable"
+                               " at bring-up (" << e.what() << "); embedded-primary ->"
+                               " deferring to embedded work source, RPC retained as"
+                               " fallback sink.";
+            }
+        } else {
+            work.set(m_rpc->getwork());
+        }
     }
 
 public:
@@ -70,10 +87,12 @@ class Node : public bch::interfaces::Node
     {
     }
 
-    void run()
+    // embedded_primary defaults false: an external-RPC-as-work-source config still
+    // hard-fails on a dead RPC at bring-up. The embedded daemon passes true.
+    void run(bool embedded_primary = false)
     {
         // RPC
-        init_rpc();
+        init_rpc(embedded_primary);
     }
 
     /// Start P2P connection to coin daemon for fast block relay.