feat: update Claude model to Opus 4.6 and enhance adaptive thinking support

- Changed model identifier from `claude-opus-4-5-20251101` to `claude-opus-4-6` across various files, including documentation and code references.
- Updated the SDK to support adaptive thinking for Opus 4.6, allowing the model to determine its own reasoning depth.
- Enhanced the thinking level options to include 'adaptive' and adjusted related components to reflect this change.
- Updated tests to ensure compatibility with the new model and its features.

These changes improve the model's capabilities and user experience by leveraging adaptive reasoning.

apps/server/src/providers/claude-provider.ts

@@ -219,8 +219,11 @@ export class ClaudeProvider extends BaseProvider {
     // claudeCompatibleProvider takes precedence over claudeApiProfile
     const providerConfig = claudeCompatibleProvider || claudeApiProfile;
 
-    // Convert thinking level to token budget
-    const maxThinkingTokens = getThinkingTokenBudget(thinkingLevel);
+    // Build thinking configuration
+    // Adaptive thinking (Opus 4.6): don't set maxThinkingTokens, model uses adaptive by default
+    // Manual thinking (Haiku/Sonnet): use budget_tokens
+    const maxThinkingTokens =
+      thinkingLevel === 'adaptive' ? undefined : getThinkingTokenBudget(thinkingLevel);
 
     // Build Claude SDK options
     const sdkOptions: Options = {
@@ -349,13 +352,13 @@ export class ClaudeProvider extends BaseProvider {
   getAvailableModels(): ModelDefinition[] {
     const models = [
       {
-        id: 'claude-opus-4-5-20251101',
-        name: 'Claude Opus 4.5',
-        modelString: 'claude-opus-4-5-20251101',
+        id: 'claude-opus-4-6',
+        name: 'Claude Opus 4.6',
+        modelString: 'claude-opus-4-6',
         provider: 'anthropic',
-        description: 'Most capable Claude model',
+        description: 'Most capable Claude model with adaptive thinking',
         contextWindow: 200000,
-        maxOutputTokens: 16000,
+        maxOutputTokens: 128000,
         supportsVision: true,
         supportsTools: true,
         tier: 'premium' as const,