F13a: add Accelerator Oscillator, Balance of Power, Choppiness Index and Vertical Horizontal Filter

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

- Rust core: accelerator_oscillator.rs (AcceleratorOscillator — AO minus a
  short SMA of itself), balance_of_power.rs (BalanceOfPower — per-bar
  (close-open)/(high-low)), choppiness_index.rs (ChoppinessIndex — summed
  true range over the high-low span, log-scaled) and
  vertical_horizontal_filter.rs (VerticalHorizontalFilter — net move over
  total move). 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
  (BalanceOfPower carries an explicit open column; VHF rides the scalar
  macros) 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 in F13c once F13b's four indicators are in.

cargo fmt + clippy (core/wickra/data/wasm/node) clean; 481 core tests,
25 data tests and 70 doctests green.

bindings/python/src/lib.rs

@@ -3856,6 +3856,253 @@ impl PyLinRegSlope {
     }
 }
 
+// ============================== Accelerator Oscillator ==============================
+
+#[pyclass(name = "AcceleratorOscillator", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyAcceleratorOscillator {
+    inner: wc::AcceleratorOscillator,
+}
+
+#[pymethods]
+impl PyAcceleratorOscillator {
+    #[new]
+    #[pyo3(signature = (ao_fast=5, ao_slow=34, signal_period=5))]
+    fn new(ao_fast: usize, ao_slow: usize, signal_period: usize) -> PyResult<Self> {
+        Ok(Self {
+            inner: wc::AcceleratorOscillator::new(ao_fast, ao_slow, signal_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 params(&self) -> (usize, usize, usize) {
+        self.inner.params()
+    }
+    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 (f, s, sig) = self.inner.params();
+        format!("AcceleratorOscillator(ao_fast={f}, ao_slow={s}, signal_period={sig})")
+    }
+}
+
+// ============================== Balance of Power ==============================
+
+#[pyclass(name = "BalanceOfPower", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyBalanceOfPower {
+    inner: wc::BalanceOfPower,
+}
+
+#[pymethods]
+impl PyBalanceOfPower {
+    #[new]
+    fn new() -> Self {
+        Self {
+            inner: wc::BalanceOfPower::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 open, high, low, close (all equal length).
+    fn batch<'py>(
+        &mut self,
+        py: Python<'py>,
+        open: PyReadonlyArray1<'py, f64>,
+        high: PyReadonlyArray1<'py, f64>,
+        low: PyReadonlyArray1<'py, f64>,
+        close: PyReadonlyArray1<'py, f64>,
+    ) -> PyResult<Bound<'py, PyArray1<f64>>> {
+        let o = open
+            .as_slice()
+            .map_err(|_| PyValueError::new_err(NON_CONTIGUOUS))?;
+        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 o.len() != h.len() || h.len() != l.len() || l.len() != c.len() {
+            return Err(PyValueError::new_err(
+                "open, high, low, close must be equal length",
+            ));
+        }
+        let mut out = Vec::with_capacity(o.len());
+        for i in 0..o.len() {
+            let candle = wc::Candle::new(o[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 {
+        "BalanceOfPower()".to_string()
+    }
+}
+
+// ============================== Choppiness Index ==============================
+
+#[pyclass(name = "ChoppinessIndex", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyChoppinessIndex {
+    inner: wc::ChoppinessIndex,
+}
+
+#[pymethods]
+impl PyChoppinessIndex {
+    #[new]
+    #[pyo3(signature = (period=14))]
+    fn new(period: usize) -> PyResult<Self> {
+        Ok(Self {
+            inner: wc::ChoppinessIndex::new(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, 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))
+    }
+    #[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!("ChoppinessIndex(period={})", self.inner.period())
+    }
+}
+
+// ============================== Vertical Horizontal Filter ==============================
+
+#[pyclass(name = "VerticalHorizontalFilter", module = "wickra._wickra")]
+#[derive(Clone)]
+struct PyVerticalHorizontalFilter {
+    inner: wc::VerticalHorizontalFilter,
+}
+
+#[pymethods]
+impl PyVerticalHorizontalFilter {
+    #[new]
+    #[pyo3(signature = (period=28))]
+    fn new(period: usize) -> PyResult<Self> {
+        Ok(Self {
+            inner: wc::VerticalHorizontalFilter::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!("VerticalHorizontalFilter(period={})", self.inner.period())
+    }
+}
+
 // ============================== Module ==============================
 
 #[pymodule]
@@ -3924,5 +4171,9 @@ fn _wickra(_py: Python<'_>, m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_class::<PyWeightedClose>()?;
     m.add_class::<PyLinearRegression>()?;
     m.add_class::<PyLinRegSlope>()?;
+    m.add_class::<PyAcceleratorOscillator>()?;
+    m.add_class::<PyBalanceOfPower>()?;
+    m.add_class::<PyChoppinessIndex>()?;
+    m.add_class::<PyVerticalHorizontalFilter>()?;
     Ok(())
 }