Milestone R0 — Restore usable IEC 61850 Browser before UX expansion #128

Purpose

Restore the user-visible application after the workbench UX regression. Recovery PR: #127. Keep validated main unchanged until verified.

Release-blocking acceptance

• Qt and Release Hardening success on the exact same final commit (not stale-head CI; verified 8b077f5e).
• Rendered QA: active tab matches canonical context and per-slot service pointers; pending multi-IED source does not mask selected IED (synthetic fixture).
• Rendered nonblank signal tree and Model Values delegate text, not merely model row counts (synthetic fixture).
• Switching/closing IED tabs preserves isolation and retains the canonical model (rendered fixture).
• Open SCL offline: IED/LD/LN/DO/DA, select/expand, FC/type/value; model survives Disconnect.
• No QML ReferenceError, TypeError, or core File/Browser/DataSet binding loop during rendered fixture smoke.
• Windows portable and installer verified from the exact accepted head (Windows release job success; artifact arstack-iec61850-workbench-windows-rc from run 36294792449).
• Real-device AA1E1F06R4 evidence for Open SCL, Discover, and signal inspection; synthetic CI alone is insufficient.
• Promote reviewed changes to main without merging the divergent UX branch wholesale.

Scope guard

Do not rewrite MMS discovery, RCB ownership, GI, static DataSet membership, or report-only runtime in a GUI recovery PR. Record evidence and links for each acceptance item.

Verified evidence (exact head 8b077f5e)

• Linux release soak: BROWSER_FLEET_ROUTING_PASS active_tab=QA_IED_B offline_signals=visible model_values=visible value_label=bound switching=pass reindex=pass cross_ied_panel=false; all Linux release-soak steps including QML runtime-error log gate, MMS reconnect and child/socket soak passed.

• Full Qt workflow and gated Windows packaging still pending at evidence-update time; do not mark R0 completed or publish as a released application until those and real-device acceptance are complete.

• Final IED Simulator Qt and Release Hardening passed on exact head 8b077f5e. Windows portable/installer artifact uploaded from same head. Remaining R0 items: hands-on Open SCL and real-device acceptance, deliberate promotion to main; not equivalent to real hardware verification.

Windows packaging evidence

• R0.1 full Release Hardening succeeded on Linux and Windows; installer and portable ZIP artifact ID 10931054253 is tied to exact head 3a3ceef9149fc0dd31b27f4c9232418a68fae0e6. Qt rendered 1024px QA also passed.
• Remaining R0 blockers: offline Open SCL GUI walkthrough evidence, AA1E1F06R4 real-device test and deliberate promotion to main. Do not close R0 from CI alone.