fix(agent): use provider registry for claw402, echo reasoning_content for thinking models, add Beta badge

- Agent now uses mcp.NewAIClientByProvider() for claw402 provider, ensuring
  x402 payment signing works correctly instead of generic HTTP client
- Added ReasoningContent field to Message/LLMResponse structs and wired
  serialization/parsing so DeepSeek thinking models work in multi-turn
- Added Beta badge to Agent nav tab in HeaderBar

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

agent/agent.go

@@ -165,13 +165,26 @@ func (a *Agent) loadAIClientFromStoreUser(storeUserID string) (mcp.AIClient, str
 			apiKey := strings.TrimSpace(string(model.APIKey))
 			customAPIURL := strings.TrimSpace(model.CustomAPIURL)
 			modelName := strings.TrimSpace(model.CustomModelName)
-			customAPIURL, modelName = resolveModelRuntimeConfig(model.Provider, customAPIURL, modelName, model.ID)
+			provider := strings.ToLower(strings.TrimSpace(model.Provider))
+
+			// Use the provider registry for providers like claw402 that have their own
+			// client implementation (x402 payment, custom auth, etc.).
+			if client := mcp.NewAIClientByProvider(provider); client != nil {
+				if modelName == "" {
+					modelName = model.ID
+				}
+				client.SetAPIKey(apiKey, customAPIURL, modelName)
+				a.log().Info("agent AI client selected (provider registry)", "store_user_id", candidateUserID, "model_id", model.ID, "provider", provider, "model", modelName)
+				return client, modelName, true
+			}
+
+			customAPIURL, modelName = resolveModelRuntimeConfig(provider, customAPIURL, modelName, model.ID)
 			if apiKey == "" || customAPIURL == "" {
 				a.log().Warn(
 					"skipping incomplete enabled AI model",
 					"store_user_id", candidateUserID,
 					"model_id", model.ID,
-					"provider", model.Provider,
+					"provider", provider,
 					"has_api_key", apiKey != "",
 					"has_custom_api_url", customAPIURL != "",
 				)

agent/planner_runtime.go

@@ -4014,6 +4014,9 @@ func (a *Agent) thinkAndActLegacyWithStore(ctx context.Context, storeUserID stri
 		if resp.Content != "" {
 			assistantMsg.Content = resp.Content
 		}
+		if resp.ReasoningContent != "" {
+			assistantMsg.ReasoningContent = resp.ReasoningContent
+		}
 		messages = append(messages, assistantMsg)
 
 		for _, tc := range resp.ToolCalls {