feat(P6/T04): WidgetAdapterSpecsController, registry, widget adapter integration

CRUD for WidgetAdapterSpec (index, show, new/create, edit/update — status+notes only
after creation). Widget new/edit forms expose optional adapter_spec_id select.
Widget show page renders adapter badge with link to spec. Widgets controller
fetches adapter spec for show action.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Web/View/Widgets/Show.hs

@@ -15,6 +15,7 @@ data ShowView = ShowView
     , recentSignals :: ![OutcomeSignal]
     , isRegressed   :: !Bool
     , cycleCount    :: !Int
+    , mAdapterSpec  :: !(Maybe WidgetAdapterSpec)
     }
 
 instance View ShowView where
@@ -54,6 +55,7 @@ instance View ShowView where
                         <span class="ml-2 text-xs bg-gray-100 px-1.5 py-0.5 rounded">{widget.policyScope}</span>
                         <span class="ml-2 text-xs bg-green-100 text-green-700 px-1.5 py-0.5 rounded">{widget.status}</span>
                         <span class="ml-2 text-xs text-gray-400">v{show widget.version}</span>
+                        {renderAdapterBadge mAdapterSpec}
                     </p>
                 </div>
                 <a href={EditWidgetAction { widgetId = widget.id }}
@@ -222,3 +224,12 @@ signalTypeClass "regressed"    = "bg-red-100 text-red-800"
 signalTypeClass "neutral"      = "bg-gray-100 text-gray-600"
 signalTypeClass "inconclusive" = "bg-yellow-100 text-yellow-800"
 signalTypeClass _              = "bg-gray-100 text-gray-600"
+
+renderAdapterBadge :: Maybe WidgetAdapterSpec -> Html
+renderAdapterBadge Nothing = mempty
+renderAdapterBadge (Just s) = [hsx|
+    <a href={ShowWidgetAdapterSpecAction { widgetAdapterSpecId = s.id }}
+       class="ml-2 text-xs bg-purple-100 text-purple-700 px-1.5 py-0.5 rounded hover:bg-purple-200">
+        adapter: {s.name}
+    </a>
+|]