Feat: Remove the exception comment field from the agent form #3221 (#9153)

### What problem does this PR solve?
Feat: Remove the exception comment field from the agent form #3221

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/pages/agent/constant.tsx

@@ -645,15 +645,23 @@ export const initialAgentValues = {
   ...initialLlmBaseValues,
   description: '',
   user_prompt: '',
-  sys_prompt: ``,
+  sys_prompt: `<role>
+  You are {{agent_name}}, an AI assistant specialized in {{domain_or_task}}.
+</role>
+<instructions>
+  1. Understand the user’s request.  
+  2. Decompose it into logical subtasks.  
+  3. Execute each subtask step by step, reasoning transparently.  
+  4. Validate accuracy and consistency.  
+  5. Summarize the final result clearly.
+</instructions>`,
   prompts: [{ role: PromptRole.User, content: `{${AgentGlobals.SysQuery}}` }],
   message_history_window_size: 12,
   max_retries: 3,
   delay_after_error: 1,
   visual_files_var: '',
   max_rounds: 5,
-  exception_method: null,
-  exception_comment: '',
+  exception_method: '',
   exception_goto: [],
   exception_default_value: '',
   tools: [],
@@ -944,5 +952,4 @@ export enum VariableType {
 export enum AgentExceptionMethod {
   Comment = 'comment',
   Goto = 'goto',
-  Null = 'null',
 }