Initial commit: Rust PDF-to-Markdown library

- Smart PDF type detection (text vs scanned) without full document load
- Text extraction using lopdf directly
- Markdown conversion with header/list/code detection
- CLI tools: detect-pdf, pdf2md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/bin/detect_pdf.rs

@@ -0,0 +1,94 @@
+//! CLI tool for detecting PDF type (text-based vs scanned)
+
+use pdf_to_markdown::{detect_pdf_type, PdfType};
+use std::env;
+use std::process;
+use std::time::Instant;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() < 2 {
+        eprintln!("Usage: {} <pdf_file>", args[0]);
+        eprintln!("       {} <pdf_file> --json", args[0]);
+        process::exit(1);
+    }
+
+    let pdf_path = &args[1];
+    let json_output = args.get(2).map(|a| a == "--json").unwrap_or(false);
+
+    let start = Instant::now();
+
+    match detect_pdf_type(pdf_path) {
+        Ok(result) => {
+            let elapsed = start.elapsed();
+
+            if json_output {
+                println!(
+                    r#"{{"pdf_type":"{}","page_count":{},"pages_sampled":{},"pages_with_text":{},"confidence":{:.2},"title":{},"detection_time_ms":{}}}"#,
+                    match result.pdf_type {
+                        PdfType::TextBased => "text_based",
+                        PdfType::Scanned => "scanned",
+                        PdfType::ImageBased => "image_based",
+                        PdfType::Mixed => "mixed",
+                    },
+                    result.page_count,
+                    result.pages_sampled,
+                    result.pages_with_text,
+                    result.confidence,
+                    result.title.as_ref().map(|t| format!("\"{}\"", t.replace('"', "\\\""))).unwrap_or_else(|| "null".to_string()),
+                    elapsed.as_millis()
+                );
+            } else {
+                println!("PDF Type Detection Results");
+                println!("==========================");
+                println!("File: {}", pdf_path);
+                println!();
+                println!(
+                    "Type: {}",
+                    match result.pdf_type {
+                        PdfType::TextBased => "TEXT-BASED (extractable text)",
+                        PdfType::Scanned => "SCANNED (OCR needed)",
+                        PdfType::ImageBased => "IMAGE-BASED (mostly images, OCR may help)",
+                        PdfType::Mixed => "MIXED (some text, some images)",
+                    }
+                );
+                println!("Confidence: {:.0}%", result.confidence * 100.0);
+                println!();
+                println!("Page count: {}", result.page_count);
+                println!("Pages sampled: {}", result.pages_sampled);
+                println!("Pages with text: {}", result.pages_with_text);
+                if let Some(title) = &result.title {
+                    println!("Title: {}", title);
+                }
+                println!();
+                println!("Detection time: {}ms", elapsed.as_millis());
+                println!();
+
+                // Recommendations
+                match result.pdf_type {
+                    PdfType::TextBased => {
+                        println!("Recommendation: Use direct text extraction (fast)");
+                    }
+                    PdfType::Scanned => {
+                        println!("Recommendation: Use OCR (MinerU or similar)");
+                    }
+                    PdfType::ImageBased => {
+                        println!("Recommendation: Use OCR for best results");
+                    }
+                    PdfType::Mixed => {
+                        println!("Recommendation: Try text extraction first, use OCR for image pages");
+                    }
+                }
+            }
+        }
+        Err(e) => {
+            if json_output {
+                println!(r#"{{"error":"{}"}}"#, e);
+            } else {
+                eprintln!("Error: {}", e);
+            }
+            process::exit(1);
+        }
+    }
+}