test(r2-12): document + patch-align the xunit v2 holdout pin (07/C-4)

Branch B (upstream-blocked): probed nuget.org for an xunit.v3 Akka TestKit —
Akka.TestKit.Xunit3 and Akka.TestKit.Xunit.v3 both return BlobNotFound (verified
2026-07-13), so the 3 holdouts (AdminUI/ControlPlane/Runtime.Tests) cannot migrate
off xunit v2 yet. Bumped the pin 2.9.2 -> 2.9.3 (latest 2.9.x) and moved the blocker
rationale + removal condition to a comment at the pin in Directory.Packages.props so
it lives at the version, not just in 3 scattered csprojs. All 3 suites green on 2.9.3
(514 + 63 + 364 tests).

Directory.Packages.props

@@ -105,7 +105,12 @@
          Avalonia.X11 (Linux desktop). Pin to the patched 0.21.3 in the same 0.x line.
          Applied via a direct PackageReference in the consuming desktop project(s). -->
     <PackageVersion Include="Tmds.DBus.Protocol" Version="0.21.3" />
-    <PackageVersion Include="xunit" Version="2.9.2" />
+    <!-- xunit v2 pin: AdminUI.Tests / ControlPlane.Tests / Runtime.Tests are held on v2 by
+         Akka.TestKit.Xunit2 (no xunit.v3 TestKit ships as of Akka 1.5.62 — both candidate ids
+         Akka.TestKit.Xunit3 / Akka.TestKit.Xunit.v3 return BlobNotFound on nuget.org, verified
+         2026-07-13). All 44 other test projects are on xunit.v3 1.1.0. Remove this pin and migrate
+         the 3 holdouts when Akka ships an xunit.v3 TestKit. (R2-12 / 07/C-4.) -->
+    <PackageVersion Include="xunit" Version="2.9.3" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.0.2" />
     <PackageVersion Include="xunit.v3" Version="1.1.0" />
     <PackageVersion Include="ZB.MOM.WW.Health" Version="0.1.0" />

archreview/plans/R2-12-repo-hygiene-plan.md.tasks.json

@@ -12,7 +12,7 @@
     { "id": 8,  "subject": "T8: U-3 — add ack/confirm/shelve/enable/disable sections to docs/Client.CLI.md; correct command count to 13", "status": "completed", "blockedBy": [] },
     { "id": 9,  "subject": "T9a: C-5 proof — ScadaBridge sweep of StyleGuide.md + confirm no .editorconfig", "status": "completed", "blockedBy": [] },
     { "id": 10, "subject": "T9b: C-5 — StyleGuide ScadaBridge->OtOpcUa + minimal suggestion-severity .editorconfig; no new TWE warnings (Commit 4 with T8)", "status": "completed", "blockedBy": [9] },
-    { "id": 11, "subject": "T10: C-4 — probe feed for xunit-v3 Akka TestKit; Branch A migrate 3 holdouts + drop 2.9.2 pin, else Branch B bump 2.9.x + blocker comment at the pin (Commit 5)", "status": "pending", "blockedBy": [] },
+    { "id": 11, "subject": "T10: C-4 — probe feed for xunit-v3 Akka TestKit; Branch A migrate 3 holdouts + drop 2.9.2 pin, else Branch B bump 2.9.x + blocker comment at the pin (Commit 5)", "status": "completed", "blockedBy": [] },
     { "id": 12, "subject": "T11: final verification — whole-solution build+test, all hygiene assertions empty, update STATUS.md (U-9 already done, do not re-plan)", "status": "pending", "blockedBy": [1, 3, 5, 7, 8, 10, 11] }
   ],
   "lastUpdated": "2026-07-12"