fix(rdkit): correct FractionCSP3 / CalcFractionCSP3 casing in docs (fixes #242)

Descriptors.FractionCsp3 and rdMolDescriptors.CalcFractionCsp3 do not
exist in RDKit 2026.03.x — the valid APIs are FractionCSP3 and
CalcFractionCSP3 (and Lipinski.FractionCSP3). Update
descriptors_reference.md (section title, usage example and diversity
helper) and api_reference.md. Bump skill metadata.version 1.2 -> 1.3.

Author: yunaremaia

skills/rdkit/SKILL.md

@@ -5,7 +5,7 @@ license: BSD-3-Clause license
 allowed-tools: Read Write Edit Bash
 compatibility: Examples target RDKit 2026.03.x. Use conda-forge for the broadest binary support or PyPI package `rdkit` for supported platform wheels; `rdkit-pypi` is the legacy PyPI name.
 metadata:
-  version: "1.2"
+  version: "1.3"
   skill-author: K-Dense Inc.
 ---
 

skills/rdkit/references/api_reference.md

@@ -249,7 +249,7 @@ Additional descriptor calculations.
 - `rdMolDescriptors.CalcNumAromaticHeterocycles(mol)` - Aromatic heterocycles
 - `rdMolDescriptors.CalcNumSpiroAtoms(mol)` - Spiro atoms
 - `rdMolDescriptors.CalcNumBridgeheadAtoms(mol)` - Bridgehead atoms
-- `rdMolDescriptors.CalcFractionCsp3(mol)` - Fraction of sp3 carbons
+- `rdMolDescriptors.CalcFractionCSP3(mol)` - Fraction of sp3 carbons
 - `rdMolDescriptors.CalcLabuteASA(mol)` - Labute accessible surface area
 - `rdMolDescriptors.CalcTPSA(mol)` - TPSA
 - `rdMolDescriptors.CalcMolFormula(mol)` - Molecular formula

skills/rdkit/references/descriptors_reference.md

@@ -197,10 +197,10 @@ Descriptors.NumAromaticAtoms(mol)
 
 ## Fraction Descriptors
 
-### FractionCsp3
+### FractionCSP3
 Fraction of carbons that are sp3 hybridized.
 ```python
-Descriptors.FractionCsp3(mol)
+Descriptors.FractionCSP3(mol)
 ```
 
 ## Complexity Descriptors
@@ -580,7 +580,7 @@ def molecular_complexity(mol):
         'BertzCT': Descriptors.BertzCT(mol),
         'NumRings': Descriptors.RingCount(mol),
         'NumRotBonds': Descriptors.NumRotatableBonds(mol),
-        'FractionCsp3': Descriptors.FractionCsp3(mol),
+        'FractionCSP3': Descriptors.FractionCSP3(mol),
         'NumAromaticRings': Descriptors.NumAromaticRings(mol)
     }
 ```