feat: add 9 Risk / Performance indicators (B18) (#218)

Adds nine risk/performance metrics to the existing **Risk / Performance** family, all consuming a per-period return series (`f64` in, `f64` out). Indicator count **498 → 507**.

## Indicators

Single-param (`new(period)`, macro bindings):
- **SterlingRatio** — mean return over average drawdown of the equity curve.
- **BurkeRatio** — return over root-sum-squared drawdowns.
- **MartinRatio** — Ulcer Performance Index; return over RMS percentage drawdown.
- **TailRatio** — 95th percentile over the absolute 5th percentile return.
- **KRatio** — Kestner; equity-curve OLS slope over the standard error of that slope.
- **CommonSenseRatio** — tail ratio times gain-to-pain.
- **GainToPainRatio** — sum of returns over the sum of absolute losses.

Multi-param (hand-written Python/Node bindings, variadic WASM macro):
- **UpsidePotentialRatio** — `new(period, mar)`; upside mean over downside deviation (Sortino philosophy).
- **M2Measure** — `new(period, risk_free, benchmark_stddev)`; Modigliani M², Sharpe rescaled into benchmark return units.

## Touchpoints
Core modules + unit tests, `mod.rs`/`lib.rs` wiring, Python/Node/WASM bindings (`index.d.ts`/`index.js` regenerated), fuzz drive lines, Python `SCALAR` registry + Node factories, CHANGELOG, and the indicator counters.

## Verification
- `cargo test -p wickra-core --lib` — 4149 passed
- `cargo test -p wickra-core --doc` — 457 passed
- `cargo clippy --workspace --all-targets --all-features -- -D warnings` — clean
- `npm test` (node) — 577 passed
- `pytest` (python) — 947 passed

bindings/python/tests/test_new_indicators.py

@@ -45,6 +45,15 @@ def ohlcv() -> tuple[np.ndarray, np.ndarray, np.ndarray, np.ndarray]:
 # --- Scalar (f64 -> f64) indicators ---------------------------------------
 
 SCALAR = [
+    (ta.M2Measure, (20, 0.0, 0.02)),
+    (ta.UpsidePotentialRatio, (20, 0.0)),
+    (ta.GainToPainRatio, (12,)),
+    (ta.CommonSenseRatio, (20,)),
+    (ta.KRatio, (30,)),
+    (ta.TailRatio, (20,)),
+    (ta.MartinRatio, (14,)),
+    (ta.BurkeRatio, (12,)),
+    (ta.SterlingRatio, (12,)),
     (ta.AUTOCORRPGRAM, (10, 48)),
     (ta.EVENBETTERSINE, (40, 10)),
     (ta.BANDPASS, (20, 0.3)),