Document best performing model for each model

[PellelNitram]

Closes #131

Summary

• Add Best model section to docs/models/word_detector.md (F1 0.8896, experiment 3, aug on, seed 42)
• Add Best model section to docs/models/simple_htr.md (CER 0.056, 84.2% word acc, experiment 3, dropout=0.5, aug on)
• Update docs/models/index.md conventions: add Best model as a required docs section and add a Best model field to the experiments log template

Test plan

• Verified WordDetector best model against experiment artifacts on GPU machine
• SimpleHTR best model confirmed from experiment log (artifacts were cleaned up after condensing into log)

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