Add three historical OCR transcription questions to HistBench

[jvpoulos]

This PR adds 3 new OCR transcription questions to HistBench, featuring historical manuscripts from different time periods, languages, and scripts. These questions test the agent's ability to transcribe historical handwriting.

New Questions Added

1. Question 415: George Washington Manuscript (18th century)
   - Source: Washington Database, line 302-15
   - Language: English
   - Script: 18th-century cursive
2. Question 416: Saint Gall Manuscript (9th century)
   - Source: Saint Gall Database, line csg562-003-02
   - Language: Latin
   - Script: Carolingian minuscule
3. Question 417: Parzival Manuscript (13th century)
   - Source: Parzival Database, line d-287b-050
   - Language: Middle High German
   - Script: Gothic

Dataset Sources & Citations

• Washington Database: A. Fischer et al. (2012). "Lexicon-Free Handwritten Word Spotting Using Character HMMs," Pattern Recognition Letters, 33(7), 934-942.
• Saint Gall Database: A. Fischer et al. (2011). "Transcription alignment of Latin manuscripts using hidden Markov models," Proc. 1st Int. Workshop on Historical Document Imaging and
  Processing, 29-36.
• Parzival Database: A. Fischer et al. (2009). "Automatic transcription of handwritten medieval documents," 15th Int. Conf. on Virtual Systems and Multimedia, 137-142.
• Attention Networks: J. Poulos & R. Valle (2021). "Character-based handwritten text transcription with attention networks," Neural Computing and Applications, 33(16), 10563-10573.