[Superseded by #41] Add portable static IEC 61850 server adapter

[masarray]

What changed

• add a separate ARIEC61850::mms_server_core library for the bounded server-side span codecs/runtime;
• add MmsStaticServerSession, an allocation-free fixed-buffer pump over an already-connected TcpByteStream;
• preserve fragmented/coalesced TPKT input and partial TCP sends across polls;
• add a WinSock/BSD desktop listener, ariec61850_static_ied_server;
• expose a read-only ESP32S3IOLD0 model with LLN0, LPHD1, and GGIO1 Ind1..Ind8;
• keep root LN TypeSpecifications available for GVAA while listing leaf variables for live-model discovery;
• add normal CTest and hard-profile wiring for connection/session regressions;
• document the lwIP/ESP-IDF integration boundary and current limitations.

Why

The portable server core already handled COTP, ACSE/MMS Initiate, static browse/read dispatch, DataSets, and reporting primitives, but it had no reusable transport session pump or runnable product adapter. This slice bridges a connected TCP stream to the core without adding WinSock, BSD sockets, lwIP, FreeRTOS, or ESP-IDF dependencies to the protocol engine.

The PR is intentionally stacked on agent/esp32p4-sv-publisher-first-trial, where the bounded static MMS server lineage currently lives. It does not touch the parallel Dynamic DataSet/Smart Dynamic RCB branches.

Validation

• MSVC Release build:
  • ariec61850_mms_server_core
  • ariec61850_static_ied_server
  • ariec61850_mms_server_session_tests
  • ariec61850_mms_connection_runtime_tests
• CTest: 3/3 passed for server session, full connection runtime, and server help contract.
• TCP loopback with the repository's own ariec61850_live_discover:
  • association and discovery succeeded;
  • 1 domain, 10 variables;
  • 1 LD, 3 LN, 10 DO, 10 DA;
  • 10 exact MMS types;
  • partial=false;
  • deterministic fingerprint 4c236411211eccc0.

Acceptance boundary

This is the first read-only runnable server adapter, not full IEC 61850 server parity or conformance. external IEC 61850 client/physical ESP32 evidence, concurrent desktop clients, GPIO-backed live snapshots, reporting/control integration, file services, TLS, and runtime SCL model loading remain follow-up slices.

[masarray]

Superseded by clean current-main successor #41.

#41 preserves the runnable read-only IEC 61850 MMS server scope and loopback evidence, adds the GCC/Clang POSIX socket type-safety fix, integrates the bounded server engine into the current embedded profile, and is based directly on current main (including #38).

This PR is retained as historical prototype/CI evidence only; its old SV/URCB/BRCB lineage should not be merged.