perf(ppvm-python-native): use mimalloc as the global allocator

crates/ppvm-python-native/Cargo.toml

@@ -10,6 +10,7 @@ crate-type = ["cdylib"]
 
 [dependencies]
 bnum = "0.13.0"
+mimalloc = { version = "0.1", default-features = false }
 num = "0.4.3"
 paste = "1.0.15"
 ppvm-runtime = { version = "0.1.0", path = "../ppvm-runtime" }

crates/ppvm-python-native/src/lib.rs

@@ -1,6 +1,13 @@
 // SPDX-FileCopyrightText: 2026 The PPVM Authors
 // SPDX-License-Identifier: Apache-2.0
 
+// Use mimalloc as the global allocator. It returns freed pages to the OS
+// more aggressively than the default system allocator, which materially
+// reduces peak RSS on the allocation-heavy Pauli-propagation paths — each
+// gate / truncation step churns large transient `Vec` / `HashMap` buffers.
+#[global_allocator]
+static GLOBAL: mimalloc::MiMalloc = mimalloc::MiMalloc;
+
 use pyo3::prelude::*;
 
 pub mod interface;