F13b: add True Range, Chaikin Volatility, Z-Score and Linear Regression Angle

Second half of the eight indicators that fill out the new family taxonomy.

- Rust core: true_range.rs (TrueRange — the raw single-bar volatility ATR
  averages), chaikin_volatility.rs (ChaikinVolatility — rate of change of a
  smoothed high-low spread), z_score.rs (ZScore — price normalised against
  its rolling mean and standard deviation) and linreg_angle.rs (LinRegAngle
  — the rolling regression slope as a degree angle). Each with a full
  Indicator impl, runnable doctest and reference / property / warmup /
  reset / batch==streaming tests.
- Python / Node / WASM: classes wired through all three bindings (ZScore
  and LinRegAngle ride the scalar macros where possible) plus .pyi stubs
  and __init__.py / __all__ entries.
- Wiki: four new Indicator-*.md pages.

The eight-family taxonomy restructure (Overview / Home / README / folder
layout) lands next in F13c.

cargo fmt + clippy (core/wickra/data/wasm/node) clean; 508 core tests,
25 data tests and 74 doctests green.

bindings/python/src/lib.rs

@@ -4103,6 +4103,228 @@ impl PyVerticalHorizontalFilter {
     }
 }
 
+// ============================== True Range ==============================
+
+#[pyclass(name = "TrueRange", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyTrueRange {
+    inner: wc::TrueRange,
+}
+
+#[pymethods]
+impl PyTrueRange {
+    #[new]
+    fn new() -> Self {
+        Self {
+            inner: wc::TrueRange::new(),
+        }
+    }
+    fn update(&mut self, candle: &Bound<'_, PyAny>) -> PyResult<Option<f64>> {
+        let c = extract_candle(candle)?;
+        Ok(self.inner.update(c))
+    }
+    /// Batch over numpy columns high, low, close (all equal length).
+    fn batch<'py>(
+        &mut self,
+        py: Python<'py>,
+        high: PyReadonlyArray1<'py, f64>,
+        low: PyReadonlyArray1<'py, f64>,
+        close: PyReadonlyArray1<'py, f64>,
+    ) -> PyResult<Bound<'py, PyArray1<f64>>> {
+        let h = high
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        let l = low
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        let c = close
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        if h.len() != l.len() || l.len() != c.len() {
+            return Err(PyValueError::new_err(
+                "high, low, close must be equal length",
+            ));
+        }
+        let mut out = Vec::with_capacity(h.len());
+        for i in 0..h.len() {
+            let candle = wc::Candle::new(c[i], h[i], l[i], c[i], 0.0, 0).map_err(map_err)?;
+            out.push(self.inner.update(candle).unwrap_or(f64::NAN));
+        }
+        Ok(out.into_pyarray_bound(py))
+    }
+    fn reset(&mut self) {
+        self.inner.reset();
+    }
+    fn is_ready(&self) -> bool {
+        self.inner.is_ready()
+    }
+    fn warmup_period(&self) -> usize {
+        self.inner.warmup_period()
+    }
+    fn __repr__(&self) -> String {
+        "TrueRange()".to_string()
+    }
+}
+
+// ============================== Chaikin Volatility ==============================
+
+#[pyclass(name = "ChaikinVolatility", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyChaikinVolatility {
+    inner: wc::ChaikinVolatility,
+}
+
+#[pymethods]
+impl PyChaikinVolatility {
+    #[new]
+    #[pyo3(signature = (ema_period=10, roc_period=10))]
+    fn new(ema_period: usize, roc_period: usize) -> PyResult<Self> {
+        Ok(Self {
+            inner: wc::ChaikinVolatility::new(ema_period, roc_period).map_err(map_err)?,
+        })
+    }
+    fn update(&mut self, candle: &Bound<'_, PyAny>) -> PyResult<Option<f64>> {
+        let c = extract_candle(candle)?;
+        Ok(self.inner.update(c))
+    }
+    /// Batch over numpy columns high, low (both equal length).
+    fn batch<'py>(
+        &mut self,
+        py: Python<'py>,
+        high: PyReadonlyArray1<'py, f64>,
+        low: PyReadonlyArray1<'py, f64>,
+    ) -> PyResult<Bound<'py, PyArray1<f64>>> {
+        let h = high
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        let l = low
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        if h.len() != l.len() {
+            return Err(PyValueError::new_err("high and low must be equal length"));
+        }
+        let mut out = Vec::with_capacity(h.len());
+        for i in 0..h.len() {
+            let candle = wc::Candle::new(l[i], h[i], l[i], l[i], 0.0, 0).map_err(map_err)?;
+            out.push(self.inner.update(candle).unwrap_or(f64::NAN));
+        }
+        Ok(out.into_pyarray_bound(py))
+    }
+    #[getter]
+    fn periods(&self) -> (usize, usize) {
+        self.inner.periods()
+    }
+    fn reset(&mut self) {
+        self.inner.reset();
+    }
+    fn is_ready(&self) -> bool {
+        self.inner.is_ready()
+    }
+    fn warmup_period(&self) -> usize {
+        self.inner.warmup_period()
+    }
+    fn __repr__(&self) -> String {
+        let (ema, roc) = self.inner.periods();
+        format!("ChaikinVolatility(ema_period={ema}, roc_period={roc})")
+    }
+}
+
+// ============================== Z-Score ==============================
+
+#[pyclass(name = "ZScore", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyZScore {
+    inner: wc::ZScore,
+}
+
+#[pymethods]
+impl PyZScore {
+    #[new]
+    #[pyo3(signature = (period=20))]
+    fn new(period: usize) -> PyResult<Self> {
+        Ok(Self {
+            inner: wc::ZScore::new(period).map_err(map_err)?,
+        })
+    }
+    fn update(&mut self, value: f64) -> Option<f64> {
+        self.inner.update(value)
+    }
+    fn batch<'py>(
+        &mut self,
+        py: Python<'py>,
+        prices: PyReadonlyArray1<'py, f64>,
+    ) -> PyResult<Bound<'py, PyArray1<f64>>> {
+        let slice = prices
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        Ok(flatten(self.inner.batch(slice)).into_pyarray_bound(py))
+    }
+    #[getter]
+    fn period(&self) -> usize {
+        self.inner.period()
+    }
+    fn reset(&mut self) {
+        self.inner.reset();
+    }
+    fn is_ready(&self) -> bool {
+        self.inner.is_ready()
+    }
+    fn warmup_period(&self) -> usize {
+        self.inner.warmup_period()
+    }
+    fn __repr__(&self) -> String {
+        format!("ZScore(period={})", self.inner.period())
+    }
+}
+
+// ============================== Linear Regression Angle ==============================
+
+#[pyclass(name = "LinRegAngle", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyLinRegAngle {
+    inner: wc::LinRegAngle,
+}
+
+#[pymethods]
+impl PyLinRegAngle {
+    #[new]
+    #[pyo3(signature = (period=14))]
+    fn new(period: usize) -> PyResult<Self> {
+        Ok(Self {
+            inner: wc::LinRegAngle::new(period).map_err(map_err)?,
+        })
+    }
+    fn update(&mut self, value: f64) -> Option<f64> {
+        self.inner.update(value)
+    }
+    fn batch<'py>(
+        &mut self,
+        py: Python<'py>,
+        prices: PyReadonlyArray1<'py, f64>,
+    ) -> PyResult<Bound<'py, PyArray1<f64>>> {
+        let slice = prices
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        Ok(flatten(self.inner.batch(slice)).into_pyarray_bound(py))
+    }
+    #[getter]
+    fn period(&self) -> usize {
+        self.inner.period()
+    }
+    fn reset(&mut self) {
+        self.inner.reset();
+    }
+    fn is_ready(&self) -> bool {
+        self.inner.is_ready()
+    }
+    fn warmup_period(&self) -> usize {
+        self.inner.warmup_period()
+    }
+    fn __repr__(&self) -> String {
+        format!("LinRegAngle(period={})", self.inner.period())
+    }
+}
+
 // ============================== Module ==============================
 
 #[pymodule]
@@ -4175,5 +4397,9 @@ fn _wickra(_py: Python<'_>, m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_class::<PyBalanceOfPower>()?;
     m.add_class::<PyChoppinessIndex>()?;
     m.add_class::<PyVerticalHorizontalFilter>()?;
+    m.add_class::<PyTrueRange>()?;
+    m.add_class::<PyChaikinVolatility>()?;
+    m.add_class::<PyZScore>()?;
+    m.add_class::<PyLinRegAngle>()?;
     Ok(())
 }