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.

crates/wickra-core/src/indicators/mod.rs

@@ -17,6 +17,7 @@ mod bollinger;
 mod bollinger_bandwidth;
 mod cci;
 mod chaikin_oscillator;
+mod chaikin_volatility;
 mod chande_kroll_stop;
 mod chandelier_exit;
 mod choppiness_index;
@@ -34,6 +35,7 @@ mod hma;
 mod kama;
 mod keltner;
 mod linreg;
+mod linreg_angle;
 mod linreg_slope;
 mod macd;
 mod mass_index;
@@ -58,6 +60,7 @@ mod t3;
 mod tema;
 mod trima;
 mod trix;
+mod true_range;
 mod tsi;
 mod typical_price;
 mod ulcer_index;
@@ -70,6 +73,7 @@ mod vwma;
 mod weighted_close;
 mod williams_r;
 mod wma;
+mod z_score;
 mod zlema;
 
 pub use accelerator_oscillator::AcceleratorOscillator;
@@ -85,6 +89,7 @@ pub use bollinger::{BollingerBands, BollingerOutput};
 pub use bollinger_bandwidth::BollingerBandwidth;
 pub use cci::Cci;
 pub use chaikin_oscillator::ChaikinOscillator;
+pub use chaikin_volatility::ChaikinVolatility;
 pub use chande_kroll_stop::{ChandeKrollStop, ChandeKrollStopOutput};
 pub use chandelier_exit::{ChandelierExit, ChandelierExitOutput};
 pub use choppiness_index::ChoppinessIndex;
@@ -102,6 +107,7 @@ pub use hma::Hma;
 pub use kama::Kama;
 pub use keltner::{Keltner, KeltnerOutput};
 pub use linreg::LinearRegression;
+pub use linreg_angle::LinRegAngle;
 pub use linreg_slope::LinRegSlope;
 pub use macd::{MacdIndicator, MacdOutput};
 pub use mass_index::MassIndex;
@@ -126,6 +132,7 @@ pub use t3::T3;
 pub use tema::Tema;
 pub use trima::Trima;
 pub use trix::Trix;
+pub use true_range::TrueRange;
 pub use tsi::Tsi;
 pub use typical_price::TypicalPrice;
 pub use ulcer_index::UlcerIndex;
@@ -138,4 +145,5 @@ pub use vwma::Vwma;
 pub use weighted_close::WeightedClose;
 pub use williams_r::WilliamsR;
 pub use wma::Wma;
+pub use z_score::ZScore;
 pub use zlema::Zlema;