feat: add RRSI (Rocket RSI) — Ehlers TASC May 2018

Algorithm: SuperSmoother-filtered momentum → Ehlers RSI → Fisher Transform
- 2-pole Butterworth IIR pre-filter removes noise
- Ehlers RSI (raw summation, not Wilder) outputs [-1,1]
- arctanh produces Gaussian-distributed zero-mean oscillator

Files: Rrsi.cs, Rrsi.Quantower.cs, Rrsi.md, 31+7 tests
Integration: sidebar, indices, Python bridge (Exports, _bridge, oscillators, SPEC)
Build: 0 warnings, 0 errors | Tests: 15,963 passed, 0 failed

lib/oscillators/rrsi/Rrsi.md

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+# Rocket RSI (RRSI)
+
+**Category:** Oscillators
+**Type:** Unbounded zero-mean oscillator
+**Author:** John F. Ehlers, TASC May 2018
+
+## Description
+
+Rocket RSI combines Ehlers' Super Smoother filter with a custom RSI calculation
+and applies the Fisher Transform to produce a Gaussian-distributed oscillator
+with sharp turning-point signals ideal for cyclic reversal detection.
+
+## Mathematical Foundation
+
+### Step 1: Half-Cycle Momentum
+$$\text{Mom}_i = \text{Close}_i - \text{Close}_{i - (\text{rsiLength} - 1)}$$
+
+### Step 2: Super Smoother Filter (2-Pole Butterworth)
+Coefficients (computed once):
+$$a_1 = e^{-1.414\pi / \text{smoothLength}}, \quad b_1 = 2 a_1 \cos(1.414\pi / \text{smoothLength})$$
+$$c_2 = b_1, \quad c_3 = -a_1^2, \quad c_1 = 1 - c_2 - c_3$$
+
+Filter:
+$$\text{Filt}_i = c_1 \cdot \frac{\text{Mom}_i + \text{Mom}_{i-1}}{2} + c_2 \cdot \text{Filt}_{i-1} + c_3 \cdot \text{Filt}_{i-2}$$
+
+### Step 3: Ehlers RSI (Normalized to ±1)
+Over the last `rsiLength` bars of filter differences:
+$$CU = \sum_{j=0}^{n-1} \max(\text{Filt}_{i-j} - \text{Filt}_{i-j-1},\ 0)$$
+$$CD = \sum_{j=0}^{n-1} \max(\text{Filt}_{i-j-1} - \text{Filt}_{i-j},\ 0)$$
+$$\text{RSI} = \frac{CU - CD}{CU + CD} \in [-1, 1]$$
+
+### Step 4: Fisher Transform
+$$\text{RocketRSI} = \frac{1}{2} \ln\left(\frac{1 + \text{clamp(RSI, \pm0.999)}}{1 - \text{clamp(RSI, \pm0.999)}}\right) = \text{arctanh}(\text{RSI})$$
+
+## Parameters
+
+| Parameter | Default | Range | Description |
+|-----------|---------|-------|-------------|
+| smoothLength | 10 | > 0 | Super Smoother filter period |
+| rsiLength | 10 | > 0 | RSI accumulation window |
+
+## Interpretation
+
+- **Values > +2**: Overbought — potential sell signal
+- **Values < −2**: Oversold — potential buy signal
+- **Zero crossings**: Momentum shift
+- **Peaks/troughs**: Cyclic turning points
+
+The Fisher Transform produces a nearly Gaussian distribution, meaning:
+- ~68% of values fall within ±1 standard deviation
+- Values beyond ±2 are statistically extreme (~5%)
+- Values beyond ±3 are very rare (~0.3%)
+
+## Key Differences from Standard RSI
+
+1. **Super Smoother pre-filter** removes high-frequency noise
+2. **Ehlers RSI** uses raw summation (not Wilder's exponential smoothing)
+3. **RSI output is ±1** (not 0–100), already suited for Fisher Transform
+4. **Fisher Transform** converts to Gaussian distribution with sharp reversals
+
+## Warmup Period
+
+`smoothLength + rsiLength` bars are needed for the IIR filter to stabilize
+and the RSI accumulation window to fill.
+
+## C# Usage
+
+```csharp
+// Streaming
+var rrsi = new Rrsi(smoothLength: 10, rsiLength: 10);
+foreach (var bar in series)
+{
+    TValue result = rrsi.Update(bar);
+    // result.Value is the Rocket RSI
+}
+
+// Batch
+TSeries results = Rrsi.Batch(series);
+
+// Span
+Rrsi.Batch(source, output, smoothLength: 10, rsiLength: 10);
+```
+
+## References
+
+- Ehlers, J. F. (2018). "Rocket RSI." *Technical Analysis of Stocks & Commodities*, May 2018.
+- Ehlers, J. F. (2004). *Cybernetic Analysis for Stocks and Futures*. Wiley.