[masarray]

Purpose

Begin M2.3 visual parity safely atop M2.2B draft #554. No data acquisition / engine / FileDirectory changes.

Implemented

• Replace visible gray 5px bar with a quiet centered 1px divider.
• When pointer hovers native splitter hitbox, divider becomes 3px near-black.
• Preserve comfortable 8px draggable hitbox without visually widening the divider.
• Retain GridSplitter as direct child of the three-column owner Grid so original native WPF resize behavior / column constraints / preview remain intact.
• Draw visual overlay with IsHitTestVisible=False; it cannot intercept drag or selection.

Acceptance

Windows native WPF compile and portable smoke on exact SHA required; screenshot/interaction QA on real Windows still pending. Both this change and upstream M1.5/M2.1/M2.2 are draft. Do not release or merge to stable without field acceptance.

[masarray]

M2.3A exact-SHA Windows acceptance — SUCCESS

HEAD 6d3a8bc7c56f9796579f5697181a5b8fac5dc8b1
Build https://github.com/masarray/arsas/actions/runs/38494876704

• Native WPF Windows build PASS.
• Immutable pinned ARIEC61850 19/19 PASS.
• ARSAS regression 1,822/1,822 PASS.
• Packaged-runtime 6/6 PASS; native ArdIrec CTest and packaged bridge PASS.
• Real portable single EXE smoke and upload PASS.
• Testable preview: ARSAS-win-x64-portable-single-exe artifact ID 11863735745.

PR #555 now contains MainWindow.xaml only. The only previous regression failure was the P109 test's literal GridSplitter Grid.Column="1" contract; attribute order fixed without changing native resize or UI behavior. CI confirms the contract passes.

No engine pin, RCB/GI, acquisition plan, static-only reporting, COMTRADE transfer or stable release was modified. Screenshot/hover/drag field QA still pending; PR stays draft.

[masarray]

Disposition: Superseded by an exact surviving WPF behavior in the authoritative integrated RC — safe administrative closure of the intermediate M2.3 GUI PR.

Canonical replacement: #727/#729 RC at 817c3910e8223fa2ac531a4426ada5d2d4bbbe50, still DRAFT and physically gated. This PR head 6d3a8bc7c56f9796579f5697181a5b8fac5dc8b1 is an exact ancestor of RC (GitHub compare ahead=1530, behind=0).

Unique delta / semantic verification: #555 modifies one file only, MainWindow.xaml, to provide the M2.3 IED Browser splitter. Inspection of the current RC MainWindow.xaml verifies the original behavior still exists: a native direct-child GridSplitter named IedBrowserPaneSplitter in Grid.Column=1 with Width=8, ShowsPreview=True, ResizeBehavior=PreviousAndNext, and a centered IsHitTestVisible=False visual overlay that is 1px idle / 3px dark on IsMouseOver. Current source retains the designed 8px WPF hitbox and cannot have the overlay intercept dragging. No unique unported production feature or independent test existed in the original PR; the initial commit and patch remain retrievable.

Safety: No branch deletion, no XAML edit, no runtime, SSOT, MMS Write/Control, ARIEC pin or public v1.6.42 change in this cleanup. This is not physical UI certification; #729 keeps full exact-head Windows, operator GUI and interoperability R7/R10 gates.

Follow-up: Maintain splitter resize behavior through current GUI/RC regression acceptance and preserve active P0/P1 shared-theme work #730/#732. No rebase or reverse-merge from this older branch.