feat(cfo): add Chande Forecast Oscillator

100 * (close - LinReg(close, period)) / close. Positive when close
overshoots the linear forecast, negative when it undershoots. Holds
the previous value if the close is zero (percentage form undefined).
Single param period (default 14).

Touchpoints: cfo.rs + mod.rs + lib.rs re-export, PyCfo + __init__.py
+ test_new_indicators SCALAR + test_known_values linear reference,
CfoNode + index.d.ts/index.js + indicators.test.js factory + reference,
WasmCfo via scalar macro, scalar-fuzz target, README + CHANGELOG.

bindings/node/src/lib.rs

@@ -1120,6 +1120,40 @@ impl AwesomeOscillatorHistogramNode {
     }
 }
 
+#[napi(js_name = "CFO")]
+pub struct CfoNode {
+    inner: wc::Cfo,
+}
+#[napi]
+impl CfoNode {
+    #[napi(constructor)]
+    pub fn new(period: u32) -> napi::Result<Self> {
+        Ok(Self {
+            inner: wc::Cfo::new(clamp_period(period)).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
+    }
+}
+
 #[napi(js_name = "APO")]
 pub struct ApoNode {
     inner: wc::Apo,