B7: give Python ROC and TRIX constructor defaults

Every other Python momentum indicator (RSI, CCI, ...) carries a
#[pyo3(signature)] default, but ROC and TRIX required an explicit
period. Both now default to the TA-Lib convention (ROC period=10, TRIX
period=30), and the .pyi stubs reflect the defaults. Node and WASM
constructors deliberately stay explicit-only -- napi-rs and
wasm-bindgen do not support default arguments, and every constructor in
those bindings is uniformly explicit.

bindings/python/python/wickra/__init__.pyi

@@ -190,7 +190,7 @@ class CCI:
     def period(self) -> int: ...
 
 class ROC:
-    def __init__(self, period: int) -> None: ...
+    def __init__(self, period: int = 10) -> None: ...
     def update(self, value: float) -> Optional[float]: ...
     def batch(self, prices: NDArray[np.float64]) -> NDArray[np.float64]: ...
     def reset(self) -> None: ...
@@ -242,7 +242,7 @@ class MFI:
     def warmup_period(self) -> int: ...
 
 class TRIX:
-    def __init__(self, period: int) -> None: ...
+    def __init__(self, period: int = 30) -> None: ...
     def update(self, value: float) -> Optional[float]: ...
     def batch(self, prices: NDArray[np.float64]) -> NDArray[np.float64]: ...
     def reset(self) -> None: ...

bindings/python/src/lib.rs

@@ -836,6 +836,7 @@ struct PyRoc {
 #[pymethods]
 impl PyRoc {
     #[new]
+    #[pyo3(signature = (period=10))]
     fn new(period: usize) -> PyResult<Self> {
         Ok(Self {
             inner: wc::Roc::new(period).map_err(map_err)?,
@@ -1054,6 +1055,7 @@ struct PyTrix {
 #[pymethods]
 impl PyTrix {
     #[new]
+    #[pyo3(signature = (period=30))]
     fn new(period: usize) -> PyResult<Self> {
         Ok(Self {
             inner: wc::Trix::new(period).map_err(map_err)?,