feat(family-13): add Ichimoku + Heikin-Ashi (#50)

Two new indicators in a brand-new "Ichimoku & alternative charts"
family:

- `Ichimoku` (Ichimoku Kinko Hyo): the full five-line cloud system
  (Tenkan-sen, Kijun-sen, Senkou Span A/B, Chikou Span). Classic
  (9, 26, 52, 26) defaults; configurable. Forward displacement is
  handled in an O(1) ring buffer so the visible Senkou A/B at bar n
  are the values computed at bar n-displacement.
- `HeikinAshi`: recursive candle smoothing transform emitting a
  four-field synthetic candle. Seeds ha_open from (open+close)/2 on
  the first bar.

Touchpoints: core + unit tests, mod.rs/lib.rs re-exports, Python +
Node + WASM bindings (multi-output via PyArray2 / interleaved Vec<f64>
/ Object+Float64Array), Python tests across smoke/new-indicators/
input-validation, Node parity tests, fuzz target (Candle), benches,
README family table + counter (71 -> 73, 8 -> 9 families), CHANGELOG.

Note: Renko, Kagi, and Point & Figure from the family-13 ideas list
are intentionally skipped. They are bar generators (the bar boundary
is defined by price moves, not by a fixed time interval) rather than
indicators that consume a candle stream, and belong in wickra-data
as candle/tick transforms alongside the existing tick-to-candle
aggregator and resampler.

CHANGELOG.md

@@ -8,6 +8,22 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- **Family 13 — Ichimoku & alternative charts.** Two new indicators:
+  - `Ichimoku` (Ichimoku Kinko Hyo) — the full five-line cloud system
+    (Tenkan-sen, Kijun-sen, Senkou Span A/B, Chikou Span) with the
+    classic `(9, 26, 52, 26)` defaults and configurable periods. Forward
+    displacement is handled in a streaming ring buffer so the
+    currently-visible Senkou A/B at bar *n* are the values computed
+    from bar *n − displacement*.
+  - `HeikinAshi` — the candle smoothing transform that recursively
+    averages OHLC into a four-component output (`ha_open`, `ha_high`,
+    `ha_low`, `ha_close`). Seeds `ha_open` from the first bar's
+    `(open + close) / 2`.
+
+  Exposed in all four bindings (Rust, Python, Node, WASM). Renko,
+  Kagi, and Point & Figure from the family ideas list are deferred:
+  they are custom bar generators rather than indicators and belong in
+  `wickra-data`.
 - **Family 10 — Ehlers / Cycle (DSP) indicators.** 16 new
   streaming-first indicators implementing John Ehlers'
   digital-signal-processing school of cycle analytics — a strong