Release ARSAS 1.6.24: multi-IED FAT and SIPROTEC Clock Sync

[masarray]

Purpose

Publish the merged FAT hardening, independent multi-IED FAT workflow, and SIPROTEC-compatible SNTP Clock Sync as ARSAS v1.6.24 so the combined build can be tested on a physical relay bench.

Release contents

• canonical version 1.6.24 across VERSION, Directory.Build.props, and application project metadata
• stable Windows publication request 12
• includes PR P0: harden FAT TCS / protection-27 smart finding #146: conservative FAT TCS / protection-27 smart-finding hardening
• includes PR P1: enable independent multi-IED FAT connections #147: independent per-IED FAT connection, discovery, and report monitoring while preserving single-active/device-filtered evidence journaling
• includes PR Add clean-room SNTP clock sync service #148: clean-room SNTPv4 Clock Sync with route-aware station-bus binding, Mode 4 unicast replies, Mode 5 directed broadcasts, and SIPROTEC compatibility stratum 2 / LOCL
• SNTP remains fail-open for IEC 61850 and never automatically stops or reconfigures Windows Time

Regression gate before merge

Release source must pass:

• source/license/release invariant checks
• full solution build and ARSAS regression tests
• IO List Testing focused tests
• SV evidence focused tests
• portable single-EXE publish and smoke test

After this PR is merged, the existing release-windows.yml pipeline will build the exact main source again, smoke-test portable and installer/uninstaller, generate checksums + SPDX SBOM + provenance + attestations, and publish stable v1.6.24 assets.

Field validation target

The published build is intended for real SIPROTEC bench validation. Confirm UDP/123 packets advertise stratum 2 and verify the relay clock actually converges to the laptop time. The stratum value is a SIPROTEC compatibility advertisement for commissioning, not a claim that the laptop is a GPS/PTP/stratum-1 source.

Release notes/landing metadata remain on the previously published version until v1.6.24 binaries exist; they will be synchronized after verified publication, matching the established v1.6.23 release sequence.