fix: add explicit UTF-8 encoding for FFI doc generation on Windows

Windows defaults to cp1252 encoding which cannot handle UTF-8 emoji
characters in the Rust source files. Added encoding='utf-8' to all
file open operations in the FFI documentation generation scripts.

Also improved error visibility in verify_ffi.py by capturing stderr
when the subprocess fails.

Author: xdustinface

contrib/verify_ffi.py

@@ -35,7 +35,10 @@ def generate_ffi_docs(crate_dir: Path) -> tuple[str, int, str]:
         capture_output=True,
         text=True
     )
-    return crate_dir.name, result.returncode, result.stdout
+    output = result.stdout
+    if result.returncode != 0 and result.stderr:
+        output = result.stderr
+    return crate_dir.name, result.returncode, output
 
 
 def main():

dash-spv-ffi/scripts/generate_ffi_docs.py

@@ -29,7 +29,7 @@ def extract_ffi_functions(file_path: Path) -> List[FFIFunction]:
     """
     functions: List[FFIFunction] = []
 
-    with open(file_path, 'r') as f:
+    with open(file_path, 'r', encoding='utf-8') as f:
         content = f.read()
 
     # Iterate over all #[no_mangle] attribute occurrences
@@ -370,7 +370,7 @@ def main():
 
     # Write to file
     output_file = Path(__file__).parent.parent / "FFI_API.md"
-    with open(output_file, 'w') as f:
+    with open(output_file, 'w', encoding='utf-8') as f:
         f.write(markdown)
 
     print(f"Generated FFI documentation with {len(all_functions)} functions")

key-wallet-ffi/scripts/generate_ffi_docs.py

@@ -28,7 +28,7 @@ def extract_ffi_functions(file_path: Path) -> List[FFIFunction]:
     """
     functions: List[FFIFunction] = []
 
-    with open(file_path, 'r') as f:
+    with open(file_path, 'r', encoding='utf-8') as f:
         content = f.read()
 
     for m in re.finditer(r'(?m)^\s*#\[no_mangle\]\s*$', content):
@@ -309,7 +309,7 @@ def main():
 
     # Write to file
     output_file = Path(__file__).parent.parent / "FFI_API.md"
-    with open(output_file, 'w') as f:
+    with open(output_file, 'w', encoding='utf-8') as f:
         f.write(markdown)
 
     print(f"Generated FFI documentation with {len(all_functions)} functions")