Phase 7 Stream F — Admin UI for scripts + test harness + historian diagnostics

Adds the draft-editor tab + page surface for authoring Phase 7 virtual tags and
scripted alarms, plus the /alarms/historian operator diagnostics page. Monaco loads
from CDN via a progressive-enhancement JS shim — the textarea works immediately so
the page is functional even if the CDN is unreachable.

## New services (Admin)

- ScriptService — CRUD for Script entity. SHA-256 SourceHash recomputed on save so
  Core.Scripting's CompiledScriptCache hits on re-publish of unchanged source + misses
  when the source actually changes.
- VirtualTagService — CRUD for VirtualTag, with Enabled toggle.
- ScriptedAlarmService — CRUD for ScriptedAlarm + lookup of persistent ScriptedAlarmState
  (logical-id-keyed per plan decision #14).
- ScriptTestHarnessService — pre-publish dry-run. Enforces plan decision #22: only
  inputs the DependencyExtractor identifies can be supplied. Missing / extra synthetic
  inputs surface as dedicated outcomes. Captures SetVirtualTag writes + Serilog events
  from the script so the operator can see both the output + the log output before
  publishing.
- HistorianDiagnosticsService — surfaces the local-process IAlarmHistorianSink state
  on /alarms/historian. Null sink reports Disabled + swallows retry. Live
  SqliteStoreAndForwardSink reports real queue depth + last-error + drain state and
  routes the Retry-dead-lettered button through.

## New UI

- ScriptsTab.razor (inside DraftEditor tabs) — list + create/edit/delete scripts with
  Monaco editor + dependency preview + test-harness run panel showing output + writes
  + log emissions.
- ScriptEditor.razor — reusable Monaco-backed textarea. Loads editor from CDN via
  wwwroot/js/monaco-loader.js. Textarea stays authoritative for Blazor binding; Monaco
  mirrors into it on every keystroke.
- AlarmsHistorian.razor (/alarms/historian) — queue depth + dead-letter depth + drain
  state badge + last-error banner + Retry-dead-lettered button.
- DraftEditor.razor — new "Scripts" tab.

## DI wiring

All five services registered in Program.cs. Null historian sink bound at Admin
composition time (real SqliteStoreAndForwardSink lives in the Server process).

## Tests — 13/13

Phase7ServicesTests covers:
- ScriptService: Add generates logical id + hash, Update recomputes hash on source
  change, Update same-source keeps hash (cache-hit preservation), Delete is idempotent
- VirtualTagService: round-trips trigger flags, Enabled toggle works
- ScriptedAlarmService: HistorizeToAveva defaults true per plan decision #15
- ScriptTestHarness: successful run captures output + writes, rejects missing /
  extra inputs, rejects non-literal paths, compile errors surface as Threw
- HistorianDiagnosticsService: null sink reports Disabled + retry returns 0

src/ZB.MOM.WW.OtOpcUa.Admin/Components/Pages/Clusters/ScriptEditor.razor

@@ -0,0 +1,41 @@
+@using Microsoft.AspNetCore.Components.Web
+@inject IJSRuntime JS
+
+@*
+    Monaco-backed C# code editor (Phase 7 Stream F). Progressive enhancement:
+    textarea renders immediately, Monaco mounts via JS interop after first render.
+    Monaco script tags are loaded once from the parent layout (wwwroot/js/monaco-loader.js
+    pulls the CDN bundle).
+
+    Stream F keeps the interop surface small — bind `Source` two-way, and the parent
+    tab re-renders on change for the dependency preview. The test-harness button
+    lives in the parent so one editor can drive multiple script types.
+*@
+
+<div class="script-editor">
+    <textarea class="form-control font-monospace" rows="14" spellcheck="false"
+              @bind="Source" @bind:event="oninput" id="@_editorId">@Source</textarea>
+</div>
+
+@code {
+    [Parameter] public string Source { get; set; } = string.Empty;
+    [Parameter] public EventCallback<string> SourceChanged { get; set; }
+
+    private readonly string _editorId = $"script-editor-{Guid.NewGuid():N}";
+
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (firstRender)
+        {
+            try
+            {
+                await JS.InvokeVoidAsync("otOpcUaScriptEditor.attach", _editorId);
+            }
+            catch (JSException)
+            {
+                // Monaco bundle not yet loaded on this page — textarea fallback is
+                // still functional.
+            }
+        }
+    }
+}