feat(wasm): Add nyap pratipadika support to WASM bindings

Add `nyap` field to `PratipadikaArgs` struct to support feminine stems
with nyāp pratyayas (ṭāp, ṅīp, etc.) in the WebAssembly API.

This allows JavaScript callers to correctly derive feminine nominal forms
for stems ending in -ā, -ī, -ū without needing to strip the ending and
rely on linga inference.

Example usage:
```javascript
vidyut.deriveSubantas({
  pratipadika: { nyap: 'nadI' },
  linga: 'Stri',
  vibhakti: 'Prathama',
  vacana: 'Eka',
})
// Returns: ['nadI']
```

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: bharathrao

vidyut-prakriya/src/wasm.rs

@@ -152,6 +152,7 @@ struct KrdantaArgs {
 #[derive(Serialize, Deserialize)]
 struct PratipadikaArgs {
     basic: Option<String>,
+    nyap: Option<String>,
     krdanta: Option<KrdantaArgs>,
 }
 
@@ -212,10 +213,17 @@ impl SubantaArgs {
         let pratipadika = match self.pratipadika {
             PratipadikaArgs {
                 basic: Some(basic),
+                nyap: None,
                 krdanta: None,
             } => Pratipadika::basic(Slp1String::from(basic).expect("ok")),
             PratipadikaArgs {
                 basic: None,
+                nyap: Some(nyap),
+                krdanta: None,
+            } => Pratipadika::nyap(Slp1String::from(nyap).expect("ok")),
+            PratipadikaArgs {
+                basic: None,
+                nyap: None,
                 krdanta: Some(krt),
             } => Pratipadika::Krdanta(Box::new(krt.into_rust()?)),
             // TODO: improve error handling, remove placeholder