Eliminate "Default" from thinking selector, always resolve to a real option

Like the model selector, the thinking selector now always resolves to an
actual thinking option ID instead of falling back to "Default" display text.

packages/app/src/components/agent-status-bar.test.ts

@@ -112,7 +112,7 @@ describe("resolveAgentModelSelection", () => {
 
     expect(selection.activeModelId).toBe("default");
     expect(selection.displayModel).toBe("Default (Sonnet 4.6)");
-    expect(selection.selectedThinkingId).toBeNull();
-    expect(selection.displayThinking).toBe("Default");
+    expect(selection.selectedThinkingId).toBe("low");
+    expect(selection.displayThinking).toBe("Low");
   });
 });

packages/app/src/components/agent-status-bar.tsx

@@ -166,7 +166,11 @@ function ControlledStatusBar({
     isModelLoading && (!modelOptions || modelOptions.length === 0)
       ? "Loading models..."
       : findOptionLabel(modelOptions, selectedModelId, "Select model");
-  const displayThinking = findOptionLabel(thinkingOptions, selectedThinkingOptionId, "Default");
+  const displayThinking = findOptionLabel(
+    thinkingOptions,
+    selectedThinkingOptionId,
+    thinkingOptions?.[0]?.label ?? "Unknown",
+  );
 
   const modeVisuals = selectedModeId ? getModeVisuals(provider, selectedModeId) : undefined;
   const ModeIconComponent = modeVisuals?.icon ? MODE_ICONS[modeVisuals.icon] : null;

packages/app/src/components/agent-status-bar.utils.ts

@@ -48,15 +48,15 @@ export function resolveAgentModelSelection(input: {
     selectedModel?.label ?? preferredModelId ?? fallbackModel?.label ?? "Unknown model";
 
   const thinkingOptions = selectedModel?.thinkingOptions ?? null;
-  const selectedThinkingId =
+  const resolvedThinkingId =
     explicitThinkingOptionId && explicitThinkingOptionId !== "default"
       ? explicitThinkingOptionId
       : (selectedModel?.defaultThinkingOptionId ?? null);
   const selectedThinking =
-    thinkingOptions?.find((option) => option.id === selectedThinkingId) ?? null;
-  const displayThinking =
-    selectedThinking?.label ??
-    (selectedThinkingId === "default" ? "Model default" : (selectedThinkingId ?? "Default"));
+    thinkingOptions?.find((option) => option.id === resolvedThinkingId) ?? null;
+  const effectiveThinking = selectedThinking ?? thinkingOptions?.[0] ?? null;
+  const selectedThinkingId = effectiveThinking?.id ?? null;
+  const displayThinking = effectiveThinking?.label ?? selectedThinkingId ?? "Unknown";
 
   return {
     selectedModel,

packages/app/src/hooks/use-agent-form-state.ts

@@ -161,7 +161,7 @@ function resolveThinkingOptionId(args: {
     return normalizedThinkingOptionId;
   }
 
-  return effectiveModel?.defaultThinkingOptionId ?? "";
+  return effectiveModel?.defaultThinkingOptionId ?? thinkingOptions[0]?.id ?? "";
 }
 
 /**