feat(detector): Scan all pages with early-exit for reliable classification

Change max_pages_to_sample from 5 to u32::MAX so every page is analyzed.
This prevents misclassifying Mixed PDFs as TextBased when scanned pages
fall outside the old 5-page sample window.

Add early-exit: stop scanning as soon as a non-text page is found, since
the PDF can't be purely TextBased. A 492-page mixed PDF exits after 2
pages instead of scanning all 492.

Also add title and confidence fields to PdfProcessResult for downstream
consumers (NAPI wrapper, feature-flag gating).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/integration_tests.rs

@@ -56,7 +56,7 @@ fn make_text_item_with_font(
 #[test]
 fn test_detection_config_default() {
     let config = DetectionConfig::default();
-    assert_eq!(config.max_pages_to_sample, 5);
+    assert_eq!(config.max_pages_to_sample, u32::MAX);
     assert_eq!(config.min_text_ops_per_page, 3);
     assert!((config.text_page_ratio_threshold - 0.6).abs() < 0.001);
 }
@@ -863,6 +863,8 @@ fn test_pages_needing_ocr_field_accessible() {
         page_count: 1,
         processing_time_ms: 0,
         pages_needing_ocr: vec![1, 3],
+        title: None,
+        confidence: 1.0,
     };
     assert_eq!(process_result.pages_needing_ocr, vec![1, 3]);
 }