Feature Request: Make "## Page" header optional in OCR output

[yul1024]

Description:
Currently, OCRProcessor.process_file automatically prepends ## Page to the output of each page. While this is helpful for human reading, it creates issues for downstream RAG (Retrieval-Augmented Generation) pipelines:

1. Semantic Chunking Interference: Tools like MarkdownHeaderTextSplitter treat ## as a structural boundary, causing unnecessary fragmentation of continuous text.
2. Noise in Embeddings: Frequent "Page X" strings add noise to the semantic vector representation.

Suggested Change:
Add a parameter to OCRProcessor or process_file to toggle this header:

# Current
process_file(file_path) -> always adds "## Page"

# Suggested
process_file(file_path, insert_page_headers=False)

Or allow users to customize the page separator template.