Keep provider diagnostics and model lists in sync (#1660)

* fix(server): align provider catalog diagnostics

* fix(server): preserve catalog profile models

* refactor: unify provider catalog discovery under AgentClient.fetchCatalog

Remove listModels/listModes from AgentClient and fetchModels/fetchModes
from ProviderDefinition. All provider runtime discovery now flows through
a single fetchCatalog(options) => ProviderCatalog API.

ProviderSnapshotManager.listModels/listModes remain as cached snapshot
conveniences only. Provider implementations (acp, codex, opencode, pi,
claude, mock) updated accordingly; agent-manager default model resolution
now calls fetchCatalog.

Reshape step toward issue pi-model-list-empty.

* refactor: remove remaining provider listModels/listModes runtime API residue

Migrate remaining AgentClient/provider-client implementations and tests to
fetchCatalog. Remove obsolete ListModelsOptions/ListModesOptions interfaces.
Update ProviderSnapshotManager.getProviderDiagnostic to materialize clients
via ensureClient(provider, definition) so diagnostics self-heal the settings
sheet instead of failing when providerClients[provider] is absent.

Allowed to remain: ProviderSnapshotManager.listModels/listModes as cached
snapshot readers; protocol/client legacy list_provider_models names; unrelated
local helper in create-agent-mode.

* test(server): repair test clients after fetchCatalog refactor

- Restore TestAgentClient.fetchCatalog with proper model list and resumeSession.
- Restore NativeArchiveRecordingClient and EnvProbeAgentClient removed during refactor.
- Fix ResumeCaptureClient.fetchCatalog and resumeSession.
- Fix stream-coalescing TestAgentClient.fetchCatalog shape and isAvailable.
- Mock accessible OpenCode provider in full-access mode tests so fetchCatalog does not throw.

* refactor(app): update stable discovered models ref directly during render

packages/app/src/components/provider-diagnostic-sheet.tsx

@@ -600,13 +600,20 @@ export function ProviderDiagnosticSheet({
   const modelsRefreshing = isRefreshing || providerSnapshotRefreshing;
 
   const stableDiscoveredRef = useRef<AgentModelDefinition[]>([]);
-  if (providerEntry?.models && providerEntry.models.length > 0) {
-    stableDiscoveredRef.current = providerEntry.models;
+  const currentModels = providerEntry?.models;
+  if (currentModels && currentModels.length > 0) {
+    stableDiscoveredRef.current = currentModels;
   }
-  const discoveredModels =
-    providerEntry?.models && providerEntry.models.length > 0
-      ? providerEntry.models
-      : stableDiscoveredRef.current;
+
+  const discoveredModels = useMemo(() => {
+    if (currentModels && currentModels.length > 0) {
+      return currentModels;
+    }
+    if (providerSnapshotRefreshing) {
+      return stableDiscoveredRef.current;
+    }
+    return [];
+  }, [currentModels, providerSnapshotRefreshing]);
 
   const [clockTick, setClockTick] = useState(0);
   useEffect(() => {