M4 physical closeout: independent canonical SV+PTP TAP capture, 60-min soak, and IED acceptance #30

Physical closeout for the M4 interop screening delivered in PR #29

This is a physical evidence task, not a decoder feature request. The software in #29 can replay local PCAP, compare SCL with observed SV identities, screen PTP two-step sequences, and show concise findings in WPF. It cannot create independent wire captures or prove IED subscription.

Equipment and capture authority

• Record ESP32-P4 ARStack firmware commit/manifest and its deployed canonical immutable SV profile / counter policy.
• Use independently trusted TAP or SPAN proven to preserve SV multicast and 802.1Q VLAN/PCP tags (USB-NIC mirror alone is insufficient).
• Capture both canonical multicast/SCL SV and broadcast untagged AR_DIAG_SV1 mirror; verify separate APPID, svID, MAC, VLAN and counters.
• Record Npcap/driver drop counters, capture timestamp origin, hardware/software timestamp limitations.

Simultaneous wire traffic and time semantics

• Verify 4000 and 4800 samples/s nominal profile cases, nofASDU, payload layout (4I+4V instMag/q), TEST/invalid q, counter rollover, stream restart and SCL mismatch handling.
• For current ARStack PTP production SOURCE mode, observe L2 domain0 Announce, two-step Sync/Follow_Up correlation and Pdelay_Resp upon request. Do not call class248/accuracy Unknown or smpSynch=0 a disciplined lock.
• Inspect the same independent capture with Validation → Inspect PCAP, and with the local ProcessBus.InteropCli --pcap ... --scl ...; investigate any MIRROR_ONLY/CONFLICT/INCOMPLETE_INTENT outcome.

Soak / performance / IED

• Capture mixed canonical SV + mirror + PTP continuously for at least 60 min; document frame counts, sequence anomalies, replay limits, driver drops and firmware TX-fail/missed-slot telemetry.
• Collect process CPU, memory/working set and allocations/GC on comparable baseline versus PR M1–M3 software closeout + M4 ARStack SV/PTP interop screening and quiet Validation UI #29; record selection/render responsiveness and failure recovery. scripts/measure-m4-bench.ps1 samples local CPU/memory.
• Independently verify the receiving IED/subscriber sees and accepts the canonical stream, with an authorized equipment test method.
• Retain authorized/sanitized checksum-linked PCAP, SCL version, firmware manifest, test environment and results in a controlled evidence store. Do not commit site captures/identifiers.

Acceptance rule

Mark physical M4 complete only with independently witnessed evidence and no unresolved identity/timing/quality contradictions. Passing 106/106 software tests, seeing a mirror, or obtaining WIRE_FIELDS_MATCH from a PCAP is not physical acceptance or formal IEC/IEEE conformance.

Runbook: docs/M4_ARSTACK_INTEROP_ACCEPTANCE.md.