fix(python-sdk): pass extension-module link args outside maturin

Cargo.toml

@@ -56,6 +56,7 @@ jsonschema = { version = "0.30", default-features = false }
 image = { version = "0.25", default-features = false, features = ["png", "jpeg", "gif", "webp"] }
 libc = "0.2"
 pyo3 = { version = "0.29.0", features = ["extension-module"] }
+pyo3-build-config = "0.29.0"
 pyo3-async-runtimes = { version = "0.29.0", features = ["tokio-runtime"] }
 pulldown-cmark = "0.13"
 ratatui = "0.30"

crates/merry-py/Cargo.toml

@@ -26,5 +26,8 @@ serde_json.workspace = true
 tokio = { workspace = true, features = ["sync"] }
 tokio-util.workspace = true
 
+[build-dependencies]
+pyo3-build-config.workspace = true
+
 [lints]
 workspace = true

crates/merry-py/build.rs

@@ -0,0 +1,11 @@
+//! Emits the linker arguments the `_merry` extension module needs on macOS.
+//!
+//! Building as an extension module (`pyo3/extension-module`) stops PyO3 from
+//! linking `libpython`, so the macOS linker must instead leave the Python
+//! symbols to be resolved by the host interpreter when the module is loaded.
+//! PyO3 only adds those arguments for projects that ask for them, and
+//! `maturin` is not in the `cargo build` path, so the crate owns them here.
+
+fn main() {
+    pyo3_build_config::add_extension_module_link_args();
+}