Expose numeric trend segment formulas from native reconstruction models

c/set-protocol/include/set_signal.h

@@ -10,6 +10,12 @@ enum { SET_SIGNAL_POLYNOMIAL, SET_SIGNAL_LINEAR, SET_SIGNAL_PCHIP, SET_SIGNAL_SP
  * Inputs may be unsorted; duplicate times are averaged. No extrapolation.
  * meta[0..2] = original count, unique count, RMSE at original measurements.
  * endpoint=1 includes the last time; 0 samples a cyclic period [first,last).
+ * On success, workspace blocks used by host formula annotations are:
+ * work[0..2*count): sorted original interleaved x,y pairs;
+ * work[2*count..3*count): unique x normalized to [0,1];
+ * work[3*count..4*count): unique averaged y divided by max(1,max(abs(y)));
+ * work[4*count..5*count): PCHIP first / spline second derivatives in these
+ * normalized coordinates (only meta[1] entries in each unique-data block).
  * Return: 0 success, 1 bounds, 2 nonfinite/degenerate data, 3 rank deficient. */
 PCAN_ABI_API int set_signal_reconstruct(const double *x, const double *y, size_t count,
     int method, unsigned degree, size_t output_count, int endpoint,