fix: Handle c_ulong type differences between Windows and Unix in FFI

- c_ulong is u32 on Windows but u64 on Unix platforms
- Use u64::from() to convert c_ulong values to u64 safely on both platforms
- Add clippy allow for useless_conversion (necessary for cross-platform compat)
- Fixes type mismatch errors in vortex_ffi::file::vx_file_scan_options

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Signed-off-by: Claude <[email protected]>

Author: joseph-isaacs

vortex-ffi/src/file.rs

@@ -108,6 +108,7 @@ impl vx_file_scan_options {
     /// Processes FFI scan options.
     ///
     /// Extracts and converts a scan configuration from an FFI options struct.
+    #[allow(clippy::useless_conversion)] // c_ulong is u32 on Windows, u64 on Unix
     fn process_scan_options(&self, session: &VortexSession) -> VortexResult<ScanOptions> {
         // Extract field names for projection.
         let projection_expr = extract_expression(
@@ -123,7 +124,7 @@ impl vx_file_scan_options {
         )?;
 
         let row_range = (self.row_range_end > self.row_range_start)
-            .then_some(self.row_range_start..self.row_range_end);
+            .then_some(u64::from(self.row_range_start)..u64::from(self.row_range_end));
 
         let split_by = (self.split_by_row_count > 0)
             .then_some(SplitBy::RowCount(self.split_by_row_count as usize));
@@ -133,7 +134,7 @@ impl vx_file_scan_options {
             filter_expr,
             split_by,
             row_range,
-            row_offset: self.row_offset,
+            row_offset: u64::from(self.row_offset),
         })
     }
 }