Keep standalone agent machines out of the Virtualization Hosts thresholds list

A machine monitored only by the Pulse agent was listed under Alerts,
Thresholds, Virtualization Hosts as well as under Machines, because the
section was fed by every resource of type `agent` rather than by
provider-owned virtualization nodes.

The two rows do not share an override identity. The Machines row resolves
through `hostOverrideIdCandidates`, which prefers the agent-derived id, while
the Virtualization Hosts row reads and writes `overridesMap.get(node.id)` on
the bare resource id. A custom threshold saved from the Virtualization Hosts
row therefore landed under a key agent alerting never reads, so the machine
kept alerting on the global default with no visible reason.

The section now takes `virtualizationHostResources`, which excludes standalone
Pulse-agent resources via the existing `isPulseAgentPlatformResource`
classifier already used by the standalone page, platform navigation and the
resource drawer. Provider-owned nodes are unaffected, since they carry
provider-owner platform evidence. Those machines lose nothing: they keep their
Machines row, which is the one alerting honours.

Reported via support by a customer whose cloud host kept firing at the 85%
global agent memory limit despite a 100% override saved on the wrong row.

frontend-modern/src/features/alerts/AlertsConfigurationSurface.tsx

@@ -88,7 +88,7 @@ export function AlertsConfigurationSurface(props: AlertsConfigurationSurfaceProp
           pbsInstances={state.pbsInstances()}
           pmgInstances={state.pmgInstances()}
           containerRuntimes={state.containerRuntimeResources()}
-          nodes={props.byType('agent')}
+          nodes={state.virtualizationHostResources()}
           agents={state.agentResources()}
           storage={props
             .allResources()

frontend-modern/src/features/alerts/__tests__/useAlertOverridesState.test.tsx

@@ -62,6 +62,53 @@ describe('useAlertOverridesState', () => {
     expect(overviewOverrides()).toEqual(result.overrides());
   });
 
+  it('keeps standalone agent machines out of the virtualization host list while retaining provider-owned nodes', () => {
+    const [hasUnsavedChanges] = createSignal(false);
+    const [, setOverviewOverrides] = createSignal([]);
+    const resources = [
+      // A cloud box running only the Pulse agent. It belongs to the Machines tab,
+      // whose overrides resolve by agent identity, so a second row here would save
+      // an override that agent alerting never reads.
+      makeResource({
+        id: 'docker-host-gcp-01',
+        name: 'docker-host-gcp-01',
+        type: 'agent',
+        platformType: 'agent',
+        sourceType: 'agent',
+        platformData: {
+          agent: { agentId: 'agent-gcp-01', platform: 'Linux' },
+        },
+      }),
+      // A real Proxmox node must still appear under Virtualization Hosts.
+      makeResource({
+        id: 'cluster-a:pve01',
+        name: 'pve01',
+        type: 'agent',
+        platformType: 'proxmox-pve',
+        sourceType: 'api',
+        platformData: {
+          proxmox: { node: 'pve01', instance: 'cluster-a' },
+        },
+      }),
+    ];
+
+    const { result } = renderHook(() =>
+      useAlertOverridesState({
+        allResources: () => resources,
+        byType: (resourceType) => resources.filter((resource) => resource.type === resourceType),
+        children: () => [],
+        hasUnsavedChanges,
+        setOverviewOverrides,
+      }),
+    );
+
+    expect(result.virtualizationHostResources().map((resource) => resource.id)).toEqual([
+      'cluster-a:pve01',
+    ]);
+    // The standalone machine is still reachable, via the Machines tab.
+    expect(result.agentResources().map((resource) => resource.id)).toContain('docker-host-gcp-01');
+  });
+
   it('projects guest overrides without agent resources and clears stale overrides when config is emptied', async () => {
     const [hasUnsavedChanges] = createSignal(false);
     const [overviewOverrides, setOverviewOverrides] = createSignal([]);

frontend-modern/src/features/alerts/useAlertOverridesState.ts

@@ -3,7 +3,10 @@ import { createEffect, createMemo, createSignal, type Accessor } from 'solid-js'
 import type { PBSInstance, PMGInstance } from '@/types/api';
 import type { RawOverrideConfig } from '@/types/alerts';
 import type { Resource, ResourceType } from '@/types/resource';
-import { isAgentFacetInfrastructureResource } from '@/utils/agentResources';
+import {
+  isAgentFacetInfrastructureResource,
+  isPulseAgentPlatformResource,
+} from '@/utils/agentResources';
 import { pbsInstanceFromResource, pmgInstanceFromResource } from '@/utils/resourceStateAdapters';
 
 import {
@@ -48,6 +51,15 @@ export function useAlertOverridesState(props: AlertOverridesStateProps) {
     props.allResources().filter((resource) => isAgentFacetInfrastructureResource(resource)),
   );
 
+  // Standalone Pulse-agent machines are not virtualization hosts. They own a row
+  // in the Machines tab, which resolves overrides by agent identity. Leaving them
+  // in the Virtualization Hosts list gave the same machine a second row that saved
+  // overrides under the bare resource id, an identity agent alerting never reads,
+  // so the override silently did nothing.
+  const virtualizationHostResources = createMemo(() =>
+    props.byType('agent').filter((resource) => !isPulseAgentPlatformResource(resource)),
+  );
+
   const pbsInstances = createMemo<PBSInstance[]>(() =>
     props
       .allResources()
@@ -157,6 +169,7 @@ export function useAlertOverridesState(props: AlertOverridesStateProps) {
     replaceRawOverridesConfig,
     allGuests,
     agentResources,
+    virtualizationHostResources,
     containerRuntimeResources,
     pbsInstances,
     pmgInstances,

frontend-modern/src/features/alerts/useAlertsConfigurationState.ts

@@ -140,6 +140,7 @@ export function useAlertsConfigurationState(props: AlertsConfigurationSurfacePro
     ...configurationSnapshotState,
     allGuests: overridesState.allGuests,
     agentResources: overridesState.agentResources,
+    virtualizationHostResources: overridesState.virtualizationHostResources,
     containerRuntimeResources: overridesState.containerRuntimeResources,
     pbsInstances: overridesState.pbsInstances,
     pmgInstances: overridesState.pmgInstances,