F8: add Bollinger Bandwidth and %b

Completes the F8 family (Bands & channels) end to end:

- Rust core: bollinger_bandwidth.rs ((upper - lower) / middle — the
  squeeze gauge) and percent_b.rs ((price - lower) / (upper - lower) —
  price position within the bands, unclamped). Both wrap BollingerBands
  and carry a full Indicator impl, runnable doctest and reference /
  constant-series / definition-consistency / warmup / reset /
  batch==streaming tests.
- Python: PyBollingerBandwidth / PyPercentB PyO3 classes + module
  registration + .pyi stubs (defaults (20, 2.0)).
- Node: explicit BollingerBandwidthNode and PercentBNode; index.d.ts
  and index.js updated.
- WASM: WasmBollingerBandwidth / WasmPercentB via the scalar macro.
- Wiki: Indicator-BollingerBandwidth.md and Indicator-PercentB.md plus
  rows in Indicators-Overview.md and entries in Home.md.

cargo fmt + clippy (core/wickra/data/wasm/node) clean; 362 core tests,
25 data tests and 51 doctests green.

bindings/wasm/src/lib.rs

@@ -90,6 +90,8 @@ wasm_scalar_indicator!(WasmCoppock, "Coppock", wc::Coppock, roc_long: usize, roc
 wasm_scalar_indicator!(WasmStdDev, "StdDev", wc::StdDev, period: usize);
 wasm_scalar_indicator!(WasmUlcerIndex, "UlcerIndex", wc::UlcerIndex, period: usize);
 wasm_scalar_indicator!(WasmHistoricalVolatility, "HistoricalVolatility", wc::HistoricalVolatility, period: usize, trading_periods: usize);
+wasm_scalar_indicator!(WasmBollingerBandwidth, "BollingerBandwidth", wc::BollingerBandwidth, period: usize, multiplier: f64);
+wasm_scalar_indicator!(WasmPercentB, "PercentB", wc::PercentB, period: usize, multiplier: f64);
 
 // ---------- KAMA (three params) ----------