fix(daemon)+fix(client): close four fool-proofing gaps

C++ (equipment_service.hpp):
- ReportSubstrate ARRIVED: check CreateResult and return INVALID_OBJECT
  when the substrate ID already exists, instead of silently doing nothing
- ReportSubstrate/ReportModule default switch branches: return false
  (→ CANNOT_DO_NOW) for unknown enum values instead of silently accepting

Python (_client.py):
- @eq.command: raise NameError (client-side name validation) instead of
  SecsGemError (which means "daemon declined a request") — wrong type
- Module docstring: update example to show @eq.command / eq.names API

Test (test_daemon_service.cpp):
- Add duplicate-ARRIVED check (expects INVALID_OBJECT)

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

tests/test_daemon_service.cpp

@@ -774,6 +774,8 @@ TEST_CASE("ReportSubstrate (E90) and ReportModule (E157) drive the FSMs") {
 
   // Reporting on a substrate that never ARRIVED is rejected.
   CHECK(sub("WFR-GHOST", pb::SubstrateReport::AT_WORK) == pb::Ack::INVALID_OBJECT);
+  // Duplicate ARRIVED (same substrate ID already in the store) is rejected.
+  CHECK(sub("WFR-1", pb::SubstrateReport::ARRIVED) == pb::Ack::INVALID_OBJECT);
 
   auto mod = [&](const std::string& mid, pb::ModuleReport::State st) {
     grpc::ClientContext ctx;