fix(centralui): surface inherited compositions in the templates tree (followup #9)

The templates tree rendered a derived/composed member (e.g. LeftReactorSide,
derived from ReactorSide) as a flat leaf, omitting compositions it inherits
from its base (e.g. LeakTest composed onto ReactorSide). BuildCompositionLeavesFor
recursed only over a template's OWN composition rows; an inherited composition
row lives on the ancestor, and TemplateComposition has no IsInherited placeholder
(unlike attributes/alarms/scripts/native-sources), so the child's own Compositions
was empty. Same 'derived templates don't surface inherited members' family as
followups #1/#2, but for compositions. Deploy/flatten was always correct
(TemplateResolver.ResolveAllMembers walks the chain) — display-only.

Fix:
- BuildCompositionLeavesFor now renders the EFFECTIVE composition set (own +
  inherited) via EffectiveCompositionsFor, which walks the inheritance chain
  (leaf->root, child wins on InstanceName), mirroring the resolver.
- Inherited slots are flagged (TemplateTreeNode.IsInherited), badged 'inherited'
  in the label, and their context menu offers only 'Open composed template'
  (Rename/Delete edit the ancestor's slot, so suppressed on inherited nodes).
- The same inherited row can appear under several derived members (LeakTest under
  both LeftReactorSide and RightReactorSide), so composition nodes use a
  path-qualified KeyOverride to keep TreeView selection/expansion keys unique;
  recursion is cycle-guarded.

Tests: +1 bUnit (TemplatesPageTests.Renders_InheritedComposition_UnderDerivedComposedMember);
CentralUI suite 867 green; full solution builds 0/0.

Docs: Component-CentralUI.md (effective composition set in tree); known-issues
tracker #9 recorded + resolved.

Note: CentralUI change — shows on wonder-app-vd03 only after that host is redeployed.

docs/requirements/Component-CentralUI.md

@@ -38,7 +38,7 @@ Central cluster only. Sites have no user interface.
 
 ### Template Authoring (Design Role)
 - The `/design/templates` page uses a **split-pane layout**: a folder/template tree sidebar on the left and the editor on the right.
-- The tree shows nested `TemplateFolder` entities with their templates underneath; composition children render inline as leaf nodes beneath their owning template (right-click "Open composed template" reveals and selects the target).
+- The tree shows nested `TemplateFolder` entities with their templates underneath; composition children render inline beneath their owning template (right-click "Open composed template" reveals and selects the target). Compositions are shown by **effective set** (own + inherited): a derived/composed member surfaces the slots it inherits from its base — e.g. `LeakTest` composed onto base `ReactorSide` appears under each derived `…ReactorSide` member — badged **"inherited"** and read-only (Rename/Delete are offered on the base's own slot, not the inherited copy).
 - **Per-kind context menus** on folder, template, and composition nodes expose the relevant operations (new folder, new template, rename, move, delete, move to folder). Root-level folders also carry a context menu. **Folder sibling reorder** is done via **Move up / Move down** menu items (M9/T23, `ReorderTemplateFolderCommand`); drag-drop is **not implemented** (permanently deferred). Tree expansion state persists in `sessionStorage`, and deep links (`/design/templates/{id}`) reveal and select the target node.
 - A **search box** above the tree (M9/T22) filters visible nodes by substring match; it is wired to `TemplateFolderTree.Filter`.
 - The `TemplateEdit` page shows a read-only **"Inherited members" panel** (M9/T26) listing the full multi-level effective inherited member set (origin, locked state, merged HiLo config) resolved by `GetResolvedTemplateMembersCommand` / `TemplateInheritanceResolver`. A **"Base changed" banner** appears when the resolver's staleness summary indicates the parent template has changed since the child was last edited. This is read-only — no "update-derived" mutation is exposed; the child is redeployed through the normal flow to pick up base changes.