review(track0): async ContextMenu OnClick + keyboard-⋯ anchoring + focus-return; discovery-driven DriverTypeNames guard; CSV round-trip comment

Wave-0 reviewer findings (no Critical/High):
- T0-1 M: ContextMenuItem.OnClick Action→Func<Task> (kills async-void at menu call sites Wave A/B/C need); keyboard-activated ⋯ now anchors below the button instead of viewport (0,0); focus returns to trigger on close; backdrop closes on native right-click too.
- T0-3 M: guard test now discovers *DriverFactoryExtensions.Register by convention from the deployed driver assemblies instead of a hand-copied list, so a future driver lacking a constant is actually caught.
- T0-2 L: corrected the round-trip 'sole non-round-trippable shape' comment (any table whose final row is a lone empty field).

Claude-Session: https://claude.ai/code/session_01LVneM3eh1UtJxEisFXgmox

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/ContextMenu.razor.css

@@ -5,6 +5,12 @@
     display: inline;
 }
 
+/* Positioned wrap so a keyboard-opened menu can anchor below the "⋯" button. */
+.ctx-ellipsis-wrap {
+    position: relative;
+    display: inline-block;
+}
+
 /* The "⋯" fallback trigger — a compact, quiet icon button. */
 .ctx-ellipsis {
     display: inline-flex;
@@ -50,6 +56,14 @@
     outline: none;
 }
 
+/* Keyboard-opened placement: anchored just below the "⋯" trigger instead of the pointer. */
+.ctx-menu--anchored {
+    position: absolute;
+    top: 100%;
+    left: 0;
+    margin-top: 0.25rem;
+}
+
 .ctx-item {
     display: flex;
     align-items: center;