feat(microstructure): trade-sign autocorrelation, PIN, Hasbrouck information share (B15) (#212)

## B15 Microstructure — three new indicators (485 → 488)

| Indicator | Input | Output | Notes |
|-----------|-------|--------|-------|
| `TradeSignAutocorrelation` | `Trade` | `f64` ∈ [-1,1] | lag-1 autocorrelation of the signed aggressor (order-flow persistence) |
| `Pin` | `Trade` | `f64` ∈ [0,1] | probability of informed trading from rolling buy/sell imbalance (EKOP single-window estimator); `name()` = `"PIN"` |
| `HasbrouckInformationShare` | `(f64, f64)` | `f64` ∈ [0,1] | variance-ratio proxy for each venue's share of price discovery |

### Wiring
- Core structs + full unit tests (every branch).
- Hand-written Python/Node/WASM bindings for the two `Trade`-input indicators (precedent `TradeImbalance`); `node_pair_indicator!` / `wasm_pair_indicator!` macro bindings + hand Python pyclass for the pairwise Hasbrouck (precedent `RollingCorrelation`).
- Fuzz drives added to `indicator_update_trade.rs` and `indicator_update_pair.rs`.
- Dedicated Python + Node streaming-vs-batch and reference tests; Hasbrouck in the `PAIR` registry.
- README counter (3 spots) + `docs/README.md` + `FAMILIES` assert bumped to 488.

### Verify (all green, local)
- `cargo test -p wickra-core --lib`: 3991 passed
- `cargo test -p wickra-core --doc`: 438 passed
- `cargo clippy --workspace --all-targets --all-features -- -D warnings`: clean
- node: 561 passed · pytest: 926 passed

bindings/node/src/lib.rs

@@ -884,6 +884,11 @@ node_pair_indicator!(
     "BetaNeutralSpread",
     wc::BetaNeutralSpread
 );
+node_pair_indicator!(
+    HasbrouckInformationShareNode,
+    "HasbrouckInformationShare",
+    wc::HasbrouckInformationShare
+);
 
 // ============================== PairSpreadZScore ==============================
 
@@ -13739,6 +13744,108 @@ impl TradeImbalanceNode {
     }
 }
 
+// Trade-sign autocorrelation carries a `period` parameter, so it is hand-written.
+#[napi(js_name = "TradeSignAutocorrelation")]
+pub struct TradeSignAutocorrelationNode {
+    inner: wc::TradeSignAutocorrelation,
+}
+
+#[napi]
+impl TradeSignAutocorrelationNode {
+    #[napi(constructor)]
+    pub fn new(period: u32) -> napi::Result<Self> {
+        Ok(Self {
+            inner: wc::TradeSignAutocorrelation::new(period as usize).map_err(map_err)?,
+        })
+    }
+    #[napi]
+    pub fn update(&mut self, price: f64, size: f64, is_buy: bool) -> napi::Result<Option<f64>> {
+        Ok(self.inner.update(build_trade(price, size, is_buy)?))
+    }
+    #[napi]
+    pub fn batch(
+        &mut self,
+        price: Vec<f64>,
+        size: Vec<f64>,
+        is_buy: Vec<bool>,
+    ) -> napi::Result<Vec<f64>> {
+        if price.len() != size.len() || size.len() != is_buy.len() {
+            return Err(NapiError::from_reason(
+                "price, size, is_buy must be equal length".to_string(),
+            ));
+        }
+        let mut out = Vec::with_capacity(price.len());
+        for i in 0..price.len() {
+            let trade = build_trade(price[i], size[i], is_buy[i])?;
+            out.push(self.inner.update(trade).unwrap_or(f64::NAN));
+        }
+        Ok(out)
+    }
+    #[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
+    }
+}
+
+// PIN carries a `window` parameter, so it is hand-written.
+#[napi(js_name = "Pin")]
+pub struct PinNode {
+    inner: wc::Pin,
+}
+
+#[napi]
+impl PinNode {
+    #[napi(constructor)]
+    pub fn new(window: u32) -> napi::Result<Self> {
+        Ok(Self {
+            inner: wc::Pin::new(window as usize).map_err(map_err)?,
+        })
+    }
+    #[napi]
+    pub fn update(&mut self, price: f64, size: f64, is_buy: bool) -> napi::Result<Option<f64>> {
+        Ok(self.inner.update(build_trade(price, size, is_buy)?))
+    }
+    #[napi]
+    pub fn batch(
+        &mut self,
+        price: Vec<f64>,
+        size: Vec<f64>,
+        is_buy: Vec<bool>,
+    ) -> napi::Result<Vec<f64>> {
+        if price.len() != size.len() || size.len() != is_buy.len() {
+            return Err(NapiError::from_reason(
+                "price, size, is_buy must be equal length".to_string(),
+            ));
+        }
+        let mut out = Vec::with_capacity(price.len());
+        for i in 0..price.len() {
+            let trade = build_trade(price[i], size[i], is_buy[i])?;
+            out.push(self.inner.update(trade).unwrap_or(f64::NAN));
+        }
+        Ok(out)
+    }
+    #[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
+    }
+}
+
 // Order Flow Imbalance: order-book input with a `period` parameter.
 #[napi(js_name = "OrderFlowImbalance")]
 pub struct OrderFlowImbalanceNode {