Polish benchmark report: 300 DPI charts, improved reaction images, README links

- Regenerated all 6 charts at 300 DPI with professional matplotlib styling
- Donut chart for overall classification, cleaner bar charts, citation footnote
- Replaced exact-match examples with verified true-exact reactions (7, 24, 28, 39, 46)
- Larger reaction images with annotated info panels and color-coded borders
- Added benchmark report PDF and image links to README
- All version references consistent at v3.9.0

Author: asad

README.md

@@ -33,7 +33,10 @@ count orphaned-reactant internal bonds as BREAK events. RDT correctly omits thes
 (verified: 0 genuine mapping errors). On balanced reactions: **100% accuracy**.
 The 23.1% atom-index rate reflects symmetry-equivalent numbering, not chemistry errors.
 
-Detailed analysis: [`benchmark/report/golden-benchmark-report.md`](benchmark/report/golden-benchmark-report.md).
+Detailed analysis: [`benchmark/report/golden-benchmark-report.md`](benchmark/report/golden-benchmark-report.md)
+| [PDF report](benchmark/report/golden-benchmark-report.pdf)
+| [Charts](benchmark/report/charts/)
+| [Reaction images](benchmark/report/images/)
 
 *Reference: Lin A et al. Molecular Informatics 41(4):e2100138, 2022. DOI: [10.1002/minf.202100138](https://doi.org/10.1002/minf.202100138)*