Resolve issue 001: remove npy_bridge.h, use std::exp/log/sqrt directly

numpycpp author confirmed: scipy's npy_exp/npy_log/npy_sqrt are just libm,
same as std::exp/log/sqrt. No bridge needed for bit-level alignment.

Changes:
- Delete scipy/npy_bridge.h (no longer needed)
- scipy/stats.h: npy_bridge::exp → std::exp, npy_bridge::sqrt → std::sqrt,
  npy_bridge::log → std::log, remove #include "npy_bridge.h"
- scipy/ndimage.h: remove #include "npy_bridge.h" (was unused)
- scipy/transform.h: remove #include "npy_bridge.h" (was unused)

numpycpp's bridge stays as-is — it serves numpy ufunc alignment.

Author: peng.li24

scipy/ndimage.h

@@ -8,7 +8,6 @@
 #include <vector>
 #include <cstddef>
 #include "numpy/core.h"
-#include "npy_bridge.h"  // direct npy_* access, bypasses SVML
 
 namespace scipy {
 namespace ndimage {

scipy/npy_bridge.h

@@ -16,7 +16,6 @@
 #include <limits>
 #include <vector>
 #include "numpy/core.h"
-#include "npy_bridge.h"  // direct npy_* access, bypasses SVML
 
 namespace scipy::stats {
 
@@ -173,7 +172,7 @@ inline T cephes_erfc(T a) {
         return (a < T(0)) ? T(2) : T(0);
     }
 
-    z = npy_bridge::exp(z);  // exp(-a^2) via npy_exp, bypasses SVML
+    z = std::exp(z);  // exp(-a^2) — std::exp is libm, same as scipy's npy_exp
 
     T p, q;
     if (x < T(8)) {
@@ -331,8 +330,8 @@ inline T cephes_ndtri(T y0) {
     }
 
     // Tail region: sqrt(-2 * log(y)) based approximation
-    T x = npy_bridge::sqrt(T(-2) * npy_bridge::log(y));
-    T x0 = x - npy_bridge::log(x) / x;
+    T x = std::sqrt(T(-2) * std::log(y));
+    T x0 = x - std::log(x) / x;
 
     T z = T(1) / x;
     T x1;

scipy/stats.h

@@ -11,7 +11,6 @@
 #include <string>
 #include <algorithm>
 #include "numpy/core.h"
-#include "npy_bridge.h"  // direct npy_* access, bypasses SVML
 
 namespace scipy {
 namespace spatial {