new: optimise.rs which handles optimisation. also linked into the python

CHANGELOG.md

@@ -1,5 +1,18 @@
 # Changelog
 
+## [Unreleased]
+
+### Added
+- `Backtest.optimize()` — parallel grid search over a vectorised signal function.
+  Simulations run on native threads with the GIL released (`src/optimise.rs`);
+  157x faster than looping `run()` over the same grid.
+- `strategy_class` is now optional, so `Backtest(df, cash=...)` works for optimization
+- Standalone HTML reports (`Backtest.plot()`) and `examples/html_report.py`
+- Three-way speed benchmark against backtesting.py (`examples/benchmark.py`)
+
+### Fixed
+- Data access inside `next()` is O(1) per bar instead of O(n) — ~2.6x faster
+
 ## [0.1.1] - 2026-07-05
 
 ### Added