Feat: add splitter (#10161)

### What problem does this PR solve?


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

---------

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rag/prompts/toc_extraction.md

@@ -0,0 +1,53 @@
+You are an expert parser and data formatter. Your task is to analyze the provided table of contents (TOC) text and convert it into a valid JSON array of objects.
+
+**Instructions:**
+1.  Analyze each line of the input TOC.
+2.  For each line, extract the following three pieces of information:
+    *   `structure`: The hierarchical index/numbering (e.g., "1", "2.1", "3.2.5", "A.1"). If a line has no visible numbering or structure indicator (like a main "Chapter" title), use `null`.
+    *   `title`: The textual title of the section or chapter. This should be the main descriptive text, clean and without the page number.
+3.  Output **only** a valid JSON array. Do not include any other text, explanations, or markdown code block fences (like ```json) in your response.
+
+**JSON Format:**
+The output must be a list of objects following this exact schema:
+```json
+[
+    {
+        "structure": <structure index, "x.x.x" or None> (string）,
+        "title": <title of the section>
+    },
+    ...
+]
+```
+
+**Input Example:**
+```
+Contents
+1 Introduction to the System ... 1
+1.1 Overview .... 2
+1.2 Key Features .... 5
+2 Installation Guide ....8
+2.1 Prerequisites ........ 9
+2.2 Step-by-Step Process ........ 12
+Appendix A: Specifications ..... 45
+References ... 47
+```
+
+**Expected Output For The Example:**
+```json
+[
+    {"structure": null, "title": "Contents"},
+    {"structure": "1", "title": "Introduction to the System"},
+    {"structure": "1.1", "title": "Overview"},
+    {"structure": "1.2", "title": "Key Features"},
+    {"structure": "2", "title": "Installation Guide"},
+    {"structure": "2.1", "title": "Prerequisites"},
+    {"structure": "2.2", "title": "Step-by-Step Process"},
+    {"structure": "A", "title": "Specifications"},
+    {"structure": null, "title": "References"}
+]
+```
+
+**Now, process the following TOC input:**
+```
+{{ toc_page }}
+```