feat(core): B4 price oscillators (TsfOscillator, MacdHistogram, PpoHistogram) (#184)

Adds three **Price Oscillators** family indicators (420 → 423).

## Indicators

- **TsfOscillator** — `100·(close − TSF)/close`, the percentage gap of the close to the **one-bar-ahead** time-series forecast. Close-relative companion to `Cfo`, which measures the same gap against the regression value at the *current* bar; the two differ by exactly the slope term `100·b/close`.
- **MacdHistogram** — the standalone `macd − signal` bar of MACD exposed as a plain `f64` series.
- **PpoHistogram** — the Percentage Price Oscillator with its 9-period signal EMA and the resulting scale-free, zero-centered histogram (PPO itself only emits the line).

All three are scalar `f64` indicators wrapping existing, already-tested building blocks (`MacdIndicator`, `Ppo` + `Ema`, `Tsf`).

## Scope notes (VORAB-CHECK)

The B4 roadmap listed six items; three were dropped to avoid duplicates:
- *Forecast Oscillator* already ships as `Cfo`.
- *Derivative Oscillator* already ships (`DerivativeOscillator`, B2).
- *Detrended Synthetic Price* deferred — no citable formula distinct from the existing `Apo`/`Dpo`.

## Touchpoints

Core (`tsf_oscillator.rs`, `macd_histogram.rs`, `ppo_histogram.rs`) with full per-branch unit tests, `mod.rs`/`lib.rs`, python/node/wasm bindings (wasm via typed-arg macro, python/node hand-written for the multi-arg histograms), fuzz drivers, python reference + streaming-vs-batch tests, node factories, README family row + counter, CHANGELOG.

Local verify: `cargo test --workspace` green, `clippy -D warnings` clean, node 498 tests, full python suite green.

bindings/node/src/lib.rs

@@ -219,6 +219,7 @@ node_scalar_indicator!(
     "TREND_STRENGTH_INDEX",
     wc::TrendStrengthIndex
 );
+node_scalar_indicator!(TsfOscillatorNode, "TsfOscillator", wc::TsfOscillator);
 #[napi(js_name = "JumpIndicator")]
 pub struct JumpIndicatorNode {
     inner: wc::JumpIndicator,
@@ -4533,6 +4534,82 @@ impl DerivativeOscillatorNode {
     }
 }
 
+// ============================== MacdHistogram ==============================
+
+#[napi(js_name = "MacdHistogram")]
+pub struct MacdHistogramNode {
+    inner: wc::MacdHistogram,
+}
+
+#[napi]
+impl MacdHistogramNode {
+    #[napi(constructor)]
+    pub fn new(fast: u32, slow: u32, signal: u32) -> napi::Result<Self> {
+        Ok(Self {
+            inner: wc::MacdHistogram::new(fast as usize, slow as usize, signal as usize)
+                .map_err(map_err)?,
+        })
+    }
+    #[napi]
+    pub fn update(&mut self, value: f64) -> Option<f64> {
+        self.inner.update(value)
+    }
+    #[napi]
+    pub fn batch(&mut self, prices: Vec<f64>) -> Vec<f64> {
+        flatten(self.inner.batch(&prices))
+    }
+    #[napi]
+    pub fn reset(&mut self) {
+        self.inner.reset();
+    }
+    #[napi(js_name = "isReady")]
+    pub fn is_ready(&self) -> bool {
+        self.inner.is_ready()
+    }
+    #[napi(js_name = "warmupPeriod")]
+    pub fn warmup_period(&self) -> u32 {
+        self.inner.warmup_period() as u32
+    }
+}
+
+// ============================== PpoHistogram ==============================
+
+#[napi(js_name = "PpoHistogram")]
+pub struct PpoHistogramNode {
+    inner: wc::PpoHistogram,
+}
+
+#[napi]
+impl PpoHistogramNode {
+    #[napi(constructor)]
+    pub fn new(fast: u32, slow: u32, signal: u32) -> napi::Result<Self> {
+        Ok(Self {
+            inner: wc::PpoHistogram::new(fast as usize, slow as usize, signal as usize)
+                .map_err(map_err)?,
+        })
+    }
+    #[napi]
+    pub fn update(&mut self, value: f64) -> Option<f64> {
+        self.inner.update(value)
+    }
+    #[napi]
+    pub fn batch(&mut self, prices: Vec<f64>) -> Vec<f64> {
+        flatten(self.inner.batch(&prices))
+    }
+    #[napi]
+    pub fn reset(&mut self) {
+        self.inner.reset();
+    }
+    #[napi(js_name = "isReady")]
+    pub fn is_ready(&self) -> bool {
+        self.inner.is_ready()
+    }
+    #[napi(js_name = "warmupPeriod")]
+    pub fn warmup_period(&self) -> u32 {
+        self.inner.warmup_period() as u32
+    }
+}
+
 // ============================== TSI ==============================
 
 #[napi(js_name = "TSI")]