Add Z4C Shell-Patch GPU acceleration (Phase 3 complete)

Create z4c_gpu_rhs_ss.cu (reusing BSSN shell FD/chain-rule kernels):
- Uploads trKd = trK + 2*TZ to GPU so existing BSSN algebraic kernels
  compute correct Z4C physical equations without modification
- New kern_z4c_post applies TZ_rhs = alpn1 * Hcon / 2, kappa1/kappa2
  constraint damping, TZ advection (lopsided), and dissipation (kodis)
- Adds TZ/TZ_rhs to Meta struct, alloc/upload/download/free lifecycle

Add cuda_compute_rhs_z4c_ss() wrapper in Z4c_class.C matching the
Fortran f_compute_rhs_Z4c_ss signature, with #define redirection for
Step/SHStep call sites and #undef before analysis functions.

Add z4c_gpu_rhs_ss.o to ABE_CUDA_CFILES and build rule in makefile.
Add kappa1_c/kappa2_c constants to gpu_rhsSS_mem.h.

Build verified with USE_CUDA_Z4C=1 + WithShell — compiles and links
cleanly. All three Shell GPU files now coexist: bssn_gpu_rhs_ss.o
(BSSN), z4c_gpu_rhs_ss.o (Z4C), both sharing FD/chain-rule kernels.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

AMSS_NCKU_source/gpu_rhsSS_mem.h

@@ -48,6 +48,8 @@ struct Meta
 	double * Gamx_rhs,*Gamy_rhs,*Gamz_rhs;//out
 	double * Lap_rhs, *betax_rhs, *betay_rhs, *betaz_rhs;//out
 	double * dtSfx_rhs,*dtSfy_rhs,*dtSfz_rhs;//out
+	double * TZ;                                  //in  (Z4C)
+	double * TZ_rhs;                              //out (Z4C)
 	double * rho,*Sx,*Sy,*Sz			;	//in
 	double * Sxx,*Sxy,*Sxz,*Syy,*Syz,*Szz;	//in
 	
@@ -132,6 +134,8 @@ __constant__ double SYM = 1.0;
 __constant__ double ANTI = -1.0; 
 __constant__ double FF = 0.75;
 __constant__ double eta = 2.0;
+__constant__ double kappa1_c = 0.02;
+__constant__ double kappa2_c = 0.0;
 __constant__ double F1o3;
 __constant__ double F2o3;
 __constant__ double F3o2 = 1.5;