feat: add Claude Opus 4.6 model support

- Add Claude Opus 4.6 to MODEL_REGISTRY
- Model ID: anthropic.claude-opus-4-6-v1 (per official AWS/Anthropic docs)
- Inference profiles: Global and US regional cross-region inference
- Max output tokens: 128000
- Pricing: $5/1M input, $25/1M output tokens
- Supports thinking mode and prompt caching

Closes #292

Author: Donuts AI Agent

src/common/models/models.ts

@@ -667,6 +667,41 @@ const MODEL_REGISTRY: ModelConfig[] = [
     }
   },
 
+  // Claude Opus 4.6
+  {
+    baseId: 'claude-opus-4-6-v1',
+    name: 'Claude Opus 4.6',
+    provider: 'anthropic',
+    category: 'text',
+    toolUse: true,
+    maxTokensLimit: 128000,
+    supportsThinking: true,
+    inferenceProfiles: [
+      {
+        type: 'global',
+        prefix: 'global',
+        regions: ['us-west-2', 'us-east-1', 'us-east-2', 'eu-west-1', 'ap-northeast-1'],
+        displaySuffix: '(Global)'
+      },
+      {
+        type: 'regional-us',
+        prefix: 'us',
+        regions: ['us-east-1', 'us-east-2', 'us-west-1', 'us-west-2'],
+        displaySuffix: '(US)'
+      }
+    ],
+    pricing: {
+      input: 0.005,
+      output: 0.025,
+      cacheRead: 0.0005,
+      cacheWrite: 0.00625
+    },
+    cache: {
+      supported: true,
+      cacheableFields: ['messages', 'system', 'tools']
+    }
+  },
+
   // Amazon Nova Premier
   {
     baseId: 'nova-premier-v1:0',

src/renderer/src/lib/pricing/modelPricing.test.ts

@@ -79,6 +79,32 @@ test('should calculate cost for Claude Opus 4.1', () => {
   expect(actualCost).toBeCloseTo(expectedCost, 6)
 })
 
+test('should calculate cost for Claude Opus 4.6', () => {
+  const modelId = 'anthropic.claude-opus-4-6-v1'
+  const pricingCalculator = new PricingCalculator(modelId)
+
+  const inputTokens = 1000
+  const outputTokens = 500
+  const cacheReadTokens = 200
+  const cacheWriteTokens = 100
+
+  const expectedCost =
+    (inputTokens * 0.005 +
+      outputTokens * 0.025 +
+      cacheReadTokens * 0.0005 +
+      cacheWriteTokens * 0.00625) /
+    1000
+
+  const actualCost = pricingCalculator.calculateTotalCost(
+    inputTokens,
+    outputTokens,
+    cacheReadTokens,
+    cacheWriteTokens
+  )
+
+  expect(actualCost).toBeCloseTo(expectedCost, 6)
+})
+
 test('should return 0 for unknown model', () => {
   const modelId = 'unknown-model'
   const pricingCalculator = new PricingCalculator(modelId)