DGB_MIN_DAEMON_VERSION resolved against frstrtr/p2pool-dgb-scrypt
networks/digibyte.py VERSION_CHECK (oracle HEAD 22761e7): floor is
82202 (DigiByte Core 7.17.2), not the placeholder 71700. Gates the
same getnetworkinfo[version] field the oracle does, so the check is
oracle-equivalent. Closes the last [confirm-vs-oracle] on the M3
RPC transport slice.

Factor the two oracle-pinned external-RPC contract values out of rpc.cpp
into a pure, dependency-light header (coin/rpc_request.hpp) so they have a
single source of truth and can be guarded by a standalone test that does
NOT link the boost::beast/jsonrpccxx transport (never enters the dgb
OBJECT lib):

  - DGB_MIN_DAEMON_VERSION / daemon_version_acceptable(): getnetworkinfo
    [version] accept floor, conformed to oracle frstrtr/p2pool-dgb-scrypt
    VERSION_CHECK == 82202 (DigiByte Core 7.17.2).
  - make_gbt_request(): getblocktemplate body {rules:[...],algo:scrypt} --
    segwit rule mandatory, scrypt is a SEPARATE algo param, never a rule.

rpc.cpp now consumes the header (behaviour-identical: version compare and
GBT body unchanged on the wire). Adds test/rpc_request_test.cpp (8 gtest
cases) pinning the floor accept/reject boundary (82202 ok / 82201,71700
reject) and the GBT shape incl. the Path-A scrypt-as-rule regression.

Standalone build-verified: g++ -std=c++20, link libgtest -> 8/8 PASS;
rpc.cpp -fsyntax-only EXIT=0. No CMake/OBJECT-lib wiring (deferred post
land-stack); additive coin-layer source only.

Pin collect_softfork_names() (softfork_check.hpp) across all three
getblockchaininfo softfork encodings (array-of-objects / array-of-strings /
object-keyed) plus accumulation + scalar no-op robustness. Guards the
softfork-gate parser NodeRPC uses to confirm segwit before trusting the
Scrypt GBT path, BEFORE the deferred post-#145 wiring CI-links rpc.cpp.

Header-only + nlohmann + gtest, no transport link -- standalone, does not
enter the dgb OBJECT lib.

Factor the DigiByte genesis hashes NodeRPC::check() probes out of rpc.cpp
into the rpc_request.hpp SSOT (DGB_GENESIS_MAIN/TEST + dgb_genesis_hash()
selector), mirroring how the daemon-version floor was made SSOT+guarded.
rpc.cpp now consumes them; the genesis hashes are a bucket-1 isolation
primitive (coin-identity, KEEP per-coin v36/v37, never standardized) --
pinned here only so a standalone TU can guard them.

Add test/genesis_check_test.cpp (7 cases): canonical mainnet/testnet
hashes, main != test (no copy/paste), 64-hex shape, and the IS_TESTNET
selector NodeRPC::check() relies on. Links only the pure SSOT header +
gtest -- no boost::beast transport, builds standalone (7/7 PASS).

CMake/OBJECT-lib registration of this test deferred to the post-#145 base
with the rest of the transport wiring.

Register the three standalone M3 regression guards
(rpc_request_test / softfork_check_test / genesis_check_test) as ctest
targets in src/impl/dgb/test/CMakeLists.txt and add them to BOTH
build.yml --target allowlists. Header-only: each links only GTest +
nlohmann_json (no OBJECT lib), so they stay buildable while the
external-daemon transport rpc.cpp wiring remains deferred (Option-B).

Avoids the #143 NOT_BUILT trap: a gtest target present in CMake but
absent from the build.yml allowlist becomes a NOT_BUILT sentinel that
reds master. Both lists, always.

23/23 guard assertions pass (rpc-request 8, softfork 8, genesis 7).