F6: add Aroon Oscillator, Vortex and Mass Index

Completes the F6 family (Trend strength) end to end:

- Rust core: aroon_oscillator.rs (AroonUp - AroonDown, one-line trend
  gauge), vortex.rs (Vortex Indicator VI+/VI- with the VortexOutput
  struct), mass_index.rs (Dorsey's range-expansion sum of the
  EMA-of-range ratio). Each with a full Indicator impl, runnable doctest
  and reference / saturation / warmup / reset / batch==streaming tests.
- Python: PyAroonOscillator / PyVortex / PyMassIndex PyO3 classes +
  module registration + .pyi stubs (defaults Aroon=14, Vortex=14,
  MassIndex=(9,25)).
- Node: explicit AroonOscillatorNode, VortexNode (with VortexValue
  object) and MassIndexNode; index.d.ts and index.js updated.
- WASM: WasmAroonOscillator, WasmVortex, WasmMassIndex.
- Wiki: Indicator-AroonOscillator/Vortex/MassIndex.md plus rows in
  Indicators-Overview.md and entries in Home.md.

cargo fmt + clippy (core/wickra/data/wasm/node) clean; 320 core tests,
25 data tests and 45 doctests green.

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

@@ -6,6 +6,7 @@
 
 mod adx;
 mod aroon;
+mod aroon_oscillator;
 mod atr;
 mod awesome_oscillator;
 mod bollinger;
@@ -20,6 +21,7 @@ mod hma;
 mod kama;
 mod keltner;
 mod macd;
+mod mass_index;
 mod mfi;
 mod mom;
 mod obv;
@@ -38,6 +40,7 @@ mod trima;
 mod trix;
 mod tsi;
 mod ultimate_oscillator;
+mod vortex;
 mod vwap;
 mod vwma;
 mod williams_r;
@@ -46,6 +49,7 @@ mod zlema;
 
 pub use adx::{Adx, AdxOutput};
 pub use aroon::{Aroon, AroonOutput};
+pub use aroon_oscillator::AroonOscillator;
 pub use atr::Atr;
 pub use awesome_oscillator::AwesomeOscillator;
 pub use bollinger::{BollingerBands, BollingerOutput};
@@ -60,6 +64,7 @@ pub use hma::Hma;
 pub use kama::Kama;
 pub use keltner::{Keltner, KeltnerOutput};
 pub use macd::{MacdIndicator, MacdOutput};
+pub use mass_index::MassIndex;
 pub use mfi::Mfi;
 pub use mom::Mom;
 pub use obv::Obv;
@@ -78,6 +83,7 @@ pub use trima::Trima;
 pub use trix::Trix;
 pub use tsi::Tsi;
 pub use ultimate_oscillator::UltimateOscillator;
+pub use vortex::{Vortex, VortexOutput};
 pub use vwap::{RollingVwap, Vwap};
 pub use vwma::Vwma;
 pub use williams_r::WilliamsR;