Fix CI: commit git-ignored pure-bindgen tool source

.gitignore

@@ -16,6 +16,10 @@ target
 # .NET build output (from the C# binding demo)
 **/bin/
 **/obj/
+# …but NOT Rust's src/bin/ crate-binary sources (e.g. the pure-bindgen tool),
+# which the broad **/bin/ rule above would otherwise swallow.
+!**/src/bin/
+!**/src/bin/**
 
 # RustRover
 #  JetBrains specific template is maintained in a separate JetBrains.gitignore that can

crates/ffi/src/bin/pure-bindgen.rs

@@ -0,0 +1,68 @@
+//! Regenerate the committed language bindings from the `pure-ffi` C ABI.
+//!
+//! ```sh
+//! cargo run -p pure-ffi --features bindgen --bin pure-bindgen
+//! ```
+//!
+//! Emits, relative to the crate root:
+//!   * `include/pure_study.h`                 — C header (cbindgen), for
+//!                                              C consumers and csbindgen/P-Invoke.
+//!   * `bindings/csharp/PureStudyNative.g.cs` — C# P/Invoke shim (csbindgen).
+//!
+//! Kotlin/Android binds the same header via JNA (see `bindings/kotlin/`); its
+//! wrapper is hand-written rather than generated, so it is not produced here.
+//!
+//! This is a developer tool, kept out of the cdylib so a plain build /
+//! cross-compile never pulls host-only generators.
+
+use std::path::Path;
+
+fn main() {
+    let crate_dir = env!("CARGO_MANIFEST_DIR");
+    generate_c_header(crate_dir);
+    generate_csharp(crate_dir);
+    println!("bindings regenerated.");
+}
+
+fn generate_c_header(crate_dir: &str) {
+    let out = Path::new(crate_dir).join("include/pure_study.h");
+    std::fs::create_dir_all(out.parent().unwrap()).expect("create include/");
+
+    let config = cbindgen::Config {
+        language: cbindgen::Language::C,
+        pragma_once: true,
+        cpp_compat: true, // wrap in extern "C" when compiled as C++
+        documentation: true,
+        documentation_style: cbindgen::DocumentationStyle::C99,
+        header: Some(
+            "/* pure-study C ABI — GENERATED by `cargo run -p pure-ffi \
+             --features bindgen`. Do not edit by hand. */"
+                .to_string(),
+        ),
+        usize_is_size_t: true,
+        ..Default::default()
+    };
+
+    cbindgen::Builder::new()
+        .with_crate(crate_dir)
+        .with_config(config)
+        .generate()
+        .expect("cbindgen: generate C header")
+        .write_to_file(&out);
+    println!("wrote {}", out.display());
+}
+
+fn generate_csharp(crate_dir: &str) {
+    let out = Path::new(crate_dir).join("bindings/csharp/PureStudyNative.g.cs");
+    std::fs::create_dir_all(out.parent().unwrap()).expect("create bindings/csharp/");
+
+    csbindgen::Builder::default()
+        .input_extern_file(Path::new(crate_dir).join("src/lib.rs"))
+        .csharp_class_name("PureStudyNative")
+        .csharp_dll_name("pure_ffi")
+        .csharp_namespace("PureStudy.Native")
+        .csharp_class_accessibility("public")
+        .generate_csharp_file(&out)
+        .expect("csbindgen: generate C# bindings");
+    println!("wrote {}", out.display());
+}