Fix code quality: trailing whitespace, unused imports, clippy warnings

- Fix trailing whitespace in kex.rs and s3.rs
- Add missing KexProposal import in kex_complete.rs
- Auto-fix clippy warnings across all crates
- All 153 tests pass

markbase-fuse/build.rs

@@ -2,15 +2,15 @@ fn main() {
     if cfg!(target_os = "macos") {
         // Link fuse-t library
         println!("cargo:rustc-link-lib=fuse-t");
-        
+
         // Link macOS frameworks
         println!("cargo:rustc-link-lib=framework=DiskArbitration");
         println!("cargo:rustc-link-lib=framework=CoreFoundation");
-        
+
         // Add fuse-t include path
         println!("cargo:rustc-link-search=native=/usr/local/lib");
-        
+
         // Rerun if fuse-t changes
         println!("cargo:rerun-if-changed=/usr/local/lib/libfuse-t.dylib");
     }
-}
+}