fix(agents): use isPrimaryMode consistently across all agent pickers (#1713)

* fix(agents): use isPrimaryMode filter for agent picker

Fix #1527: agent picker filtered by mode !== 'subagent' which missed
agents with unexpected mode values. Now uses isPrimaryMode() which
only includes 'primary', 'all', undefined, and null — the semantically
correct set of agents that should appear in the picker.

* fix(agents): use isPrimaryMode consistently across all agent pickers

Updated AgentSelector.tsx to use isPrimaryMode instead of mode !== 'subagent'.
Removed duplicate isPrimaryMode definition from useConfigStore.ts and
imported the shared helper from mobileControlsUtils.

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Co-authored-by: Leonid Skorobogatyy <bash@opencode.itc.local>

packages/ui/src/stores/useConfigStore.ts

@@ -7,6 +7,7 @@ import { scopeMatches, subscribeToConfigChanges } from "@/lib/configSync";
 import type { ModelMetadata } from "@/types";
 import { getSafeStorage } from "./utils/safeStorage";
 import { filterVisibleAgents } from "./useAgentsStore";
+import { isPrimaryMode } from "@/components/chat/mobileControlsUtils";
 import { useSessionUIStore } from "@/sync/session-ui-store";
 import { useSelectionStore } from "@/sync/selection-store";
 import { getRegisteredRuntimeAPIs } from "@/contexts/runtimeAPIRegistry";
@@ -179,8 +180,6 @@ const parseModelString = (modelString: string): { providerId: string; modelId: s
 
 const normalizeProviderId = (value: string) => value?.toLowerCase?.() ?? '';
 
-const isPrimaryMode = (mode?: string) => mode === "primary" || mode === "all" || mode === undefined || mode === null;
-
 type ProviderModel = Provider["models"][string];
 type ProviderWithModelList = Omit<Provider, "models"> & { models: ProviderModel[] };