refactor(centralui): migrate TemplateEdit's four page-embedded modals to the DialogService host (M10 residual)

TemplateEdit was the last page still hand-rolling its own modal chrome after
M10 — T34c only tokenized its backdrops. All four member-authoring forms
(Attribute, Alarm, Native Alarm Source, Script) now open through
IDialogService.ShowAsync, so the single DialogHost in MainLayout owns the
backdrop, focus trap, Escape and focus restoration.

Pattern copied from the already-migrated pages (MoveDataConnectionDialog +
Templates' Move/Rename dialogs): each body is its own component beside the page
taking a DialogContext<bool>, owning its form state, rendering validation and
server errors INLINE while staying open, and closing with Close(true) only once
the save succeeded — at which point the page reloads. An inline RenderFragment
would NOT have worked: DialogHost renders the captured fragment in its own tree,
so the page's StateHasChanged could never refresh it.

Persistence deliberately stayed on the page (it owns TemplateService, the
inherited-member rules, and the repository-direct native-source path) and is
reached through an OnSaveAsync delegate returning null on success or the message
to display. Behaviour preserved verbatim, including the List-attribute encode +
Decode round-trip check, the name/trigger-type read-only-on-edit rules, the
duplicate-native-source-name guard, and NormalizeExecutionTimeout.

TemplateScriptDialog keeps all four tab panels mounted (Monaco and the JSONJoy
island must not tear down on tab switch) and hosts the Test Run panel, which
needs the live unsaved editor buffer, so it injects ScriptAnalysisService
directly and cancels an in-flight run on dispose.

Extraction moved markup that three structural source-scanning tests pinned;
all three were repointed at the new files rather than weakened:
  - TemplateNativeAlarmSourceEditorTests (+ a new test asserting the form is
    host-mounted and the body renders no chrome of its own)
  - AttributeListEditorTests (list-editor reveal now in the dialog body)
  - TestRunWarningTests (Real I/O warning travelled with the script panel)

Build 0/0; CentralUI.Tests 973/973 green.

docs/requirements/Component-CentralUI.md

@@ -47,7 +47,8 @@ Central cluster only. Sites have no user interface.
 - Manage template hierarchy (inheritance) — visual tree of parent/child relationships.
 - Manage composition — add/remove feature module instances within templates. **Naming collision detection** provides immediate feedback if composed modules introduce duplicate attribute, alarm, or script names.
 - Define and edit attributes, alarms, and scripts on templates.
-- **Native Alarms tab** (`TemplateEdit`): a tab alongside Attributes / Alarms / Scripts / Compositions that lists the template's **native alarm source bindings** — the OPC UA Alarms & Conditions / MxAccess Gateway sources whose alarm state the instance mirrors. Each binding carries Name, Connection, Source Reference, optional Condition Filter, Description, and a Lock flag. Add / edit / delete go through a **modal**:
+- **Member authoring dialogs are hosted, not page-embedded** (M10 residual, 2026-08-01): the template editor's Attribute, Alarm, Native Alarm Source, and Script forms all open through `IDialogService.ShowAsync`, so the single `DialogHost` in `MainLayout` owns the backdrop, focus trap, Escape, and focus restoration. Each form body is its own component beside the page (`TemplateAttributeDialog`, `TemplateAlarmDialog`, `TemplateNativeAlarmSourceDialog`, `TemplateScriptDialog`), following the `MoveDataConnectionDialog` pattern — the body renders validation and server errors **inline and stays open**, closing only on a successful save; persistence stays on the page (which owns `TemplateService`) behind an `OnSaveAsync` delegate.
+- **Native Alarms tab** (`TemplateEdit`): a tab alongside Attributes / Alarms / Scripts / Compositions that lists the template's **native alarm source bindings** — the OPC UA Alarms & Conditions / MxAccess Gateway sources whose alarm state the instance mirrors. Each binding carries Name, Connection, Source Reference, optional Condition Filter, Description, and a Lock flag. Add / edit / delete go through a **hosted dialog** (`TemplateNativeAlarmSourceDialog`):
   - **Name** — unique within the template (lock/inherit bookkeeping mirrors `TemplateAlarm`).
   - **Connection** — a dropdown filtered to **alarm-capable connections only** (OPC UA and MxGateway protocols).
   - **Source Reference** — the native key (OPC UA SourceNode / notifier nodeId, or MxAccess object/area).
@@ -158,7 +159,7 @@ Central cluster only. Sites have no user interface.
 
 #### Tabbed Layout
 
-The Debug View page uses a **two-tab layout** — an **Attributes** tab and an **Alarms** tab — replacing the earlier side-by-side flat tables. Each tab renders its data as a **collapsible hierarchy tree** using the existing generic `TreeView<TItem>` component.
+The Debug View page uses a **two-tab layout** — an **Attributes** tab and an **Alarms** tab — replacing the earlier side-by-side flat tables. Each tab renders its data as a **collapsible hierarchy tree** using the existing generic `TreeView<TItem>` component. As of 2026-08-01 that component implements the full **WAI-ARIA tree keyboard pattern** — roving tabindex (one Tab stop per tree), Arrow/Home/End movement, Enter/Space activation, plus `aria-level`/`aria-posinset`/`aria-setsize` — so every tree surface in the Central UI (Debug View, Data Connections, Topology, the template folder browser) is keyboard-navigable. See [`docs/components/TreeView.md`](../components/TreeView.md).
 
 **Tree hierarchy** — the hierarchy is derived from the path-qualified canonical names already present in the debug snapshot (e.g. `Motor1.Compressor.Pump`). The instance is the root node; composed modules are collapsible branch nodes; individual attributes (Attributes tab) or alarms/native-source bindings (Alarms tab) are leaf nodes.