Antiferromagnet/superconductor (AFM/SC) hybrids offer a rich but largely unexplored platform for realizing spin-triplet Cooper pairing and chiral topological superconductivity, yet experimental demonstrations remain scarce. Here, we report the modification of superconductivity in NbSe${}_2$/MnPS${}_3$ heterostructures via the AFM proximity effect. The N'eel order of MnPS${}_3$ effectively suppresses the Ising superconductivity of NbSe${}_2$ and induces a spatially inhomogeneous superconducting state with an inherent junction network. Leveraging this intrinsic Josephson coupling, we observe a finite phase offset in the critical-current interference pattern and a zero-field supercurrent diode effecttwo independent signatures of spontaneous time-reversal symmetry breaking. Supported by theoretical modeling, we attribute these emergent phenomena to the proximity-induced stabilization of a subdominant in-plane triplet pairing channel, which is distinct from the intrinsic Ising channel of NbSe${}_2$. Our findings establish AFM/SC heterostructures as a versatile platform for exploring non-reciprocal transport and open promising avenues for superconducting spintronics.