fix(delegate-task): reject primary agents in task subagent resolution

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/delegate-task/fallback-entry-settings.ts

@@ -0,0 +1,20 @@
+import type { DelegatedModelConfig } from "./types"
+import type { FallbackEntry } from "../../shared/model-requirements"
+
+export function applyFallbackEntrySettings(input: {
+  categoryModel: DelegatedModelConfig
+  effectiveEntry: FallbackEntry
+  variantOverride?: string
+}): DelegatedModelConfig {
+  const { categoryModel, effectiveEntry, variantOverride } = input
+
+  return {
+    ...categoryModel,
+    variant: variantOverride ?? effectiveEntry.variant ?? categoryModel.variant,
+    reasoningEffort: effectiveEntry.reasoningEffort ?? categoryModel.reasoningEffort,
+    temperature: effectiveEntry.temperature ?? categoryModel.temperature,
+    top_p: effectiveEntry.top_p ?? categoryModel.top_p,
+    maxTokens: effectiveEntry.maxTokens ?? categoryModel.maxTokens,
+    thinking: effectiveEntry.thinking ?? categoryModel.thinking,
+  }
+}