Feat: Redesign and refactor agent module (#9113)

### What problem does this PR solve?

#9082 #6365

<u> **WARNING: it's not compatible with the older version of `Agent`
module, which means that `Agent` from older versions can not work
anymore.**</u>

### Type of change

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

rag/prompts/reflect.md

@@ -0,0 +1,34 @@
+**Context**:
+ - To achieve the goal: {{ goal }}.
+ - You have executed following tool calls:
+{% for call in tool_calls %}
+Tool call: `{{ call.name }}`
+Results: {{ call.result }}
+{% endfor %}
+
+
+**Reflection Instructions:**
+
+Analyze the current state of the overall task ({{ goal }}), then provide structured responses to the following:
+
+## 1. Goal Achievement Status
+ - Does the current outcome align with the original purpose of this task phase? 
+ - If not, what critical gaps exist?
+
+## 2. Step Completion Check
+ - Which planned steps were completed? (List verified items)
+ - Which steps are pending/incomplete? (Specify exactly what’s missing)
+
+## 3. Information Adequacy
+ - Is the collected data sufficient to proceed?
+ - What key information is still needed? (e.g., metrics, user input, external data)
+
+## 4. Critical Observations
+ - Unexpected outcomes: [Flag anomalies/errors]
+ - Risks/blockers: [Identify immediate obstacles]
+ - Accuracy concerns: [Highlight unreliable results]
+
+## 5. Next-Step Recommendations
+ - Proposed immediate action: [Concrete next step]
+ - Alternative strategies if blocked: [Workaround solution]
+ - Tools/inputs required for next phase: [Specify resources]