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-core/src/vfs/s3_fs.rs

@@ -56,7 +56,10 @@ impl S3Vfs {
 
         let credentials = Credentials::new(access_key, secret_key);
 
-        Ok(Self { bucket, credentials })
+        Ok(Self {
+            bucket,
+            credentials,
+        })
     }
 
     fn path_to_key(path: &Path) -> String {
@@ -118,7 +121,10 @@ impl S3Vfs {
             .map_err(|e| VfsError::Io(format!("S3 PUT failed: {}", e)))?;
 
         if resp.status() != 200 {
-            return Err(VfsError::Io(format!("PutObject returned {}", resp.status())));
+            return Err(VfsError::Io(format!(
+                "PutObject returned {}",
+                resp.status()
+            )));
         }
         Ok(())
     }
@@ -149,15 +155,15 @@ impl S3Vfs {
             .map_err(|e| VfsError::Io(format!("S3 CopyObject failed: {}", e)))?;
 
         if resp.status() != 200 {
-            return Err(VfsError::Io(format!("CopyObject returned {}", resp.status())));
+            return Err(VfsError::Io(format!(
+                "CopyObject returned {}",
+                resp.status()
+            )));
         }
         Ok(())
     }
 
-    fn list_objects(
-        &self,
-        prefix: &str,
-    ) -> Result<actions::ListObjectsV2Response, VfsError> {
+    fn list_objects(&self, prefix: &str) -> Result<actions::ListObjectsV2Response, VfsError> {
         let mut action = actions::ListObjectsV2::new(&self.bucket, Some(&self.credentials));
         if !prefix.is_empty() {
             action.with_prefix(prefix);
@@ -181,9 +187,8 @@ impl S3Vfs {
             .read_to_string(&mut body)
             .map_err(|e| VfsError::Io(format!("Failed to read S3 list response: {}", e)))?;
 
-        actions::ListObjectsV2::parse_response(&body).map_err(|e| {
-            VfsError::Io(format!("Failed to parse S3 list response XML: {}", e))
-        })
+        actions::ListObjectsV2::parse_response(&body)
+            .map_err(|e| VfsError::Io(format!("Failed to parse S3 list response XML: {}", e)))
     }
 }
 
@@ -409,7 +414,9 @@ impl VfsBackend for S3Vfs {
 
 impl VfsFile for S3VfsFile {
     fn read(&mut self, buf: &mut [u8]) -> Result<usize, VfsError> {
-        let to_read = buf.len().min((self.size.saturating_sub(self.position)) as usize);
+        let to_read = buf
+            .len()
+            .min((self.size.saturating_sub(self.position)) as usize);
         if to_read == 0 {
             return Ok(0);
         }
@@ -443,7 +450,7 @@ impl VfsFile for S3VfsFile {
                     self.position = sz.saturating_add(offset as u64);
                 } else {
                     let abs = offset.unsigned_abs();
-                    self.position = if abs <= sz { sz - abs } else { 0 };
+                    self.position = sz.saturating_sub(abs);
                 }
             }
             std::io::SeekFrom::Current(offset) => {
@@ -451,11 +458,7 @@ impl VfsFile for S3VfsFile {
                     self.position = self.position.saturating_add(offset as u64);
                 } else {
                     let abs = offset.unsigned_abs();
-                    self.position = if abs <= self.position {
-                        self.position - abs
-                    } else {
-                        0
-                    };
+                    self.position = self.position.saturating_sub(abs);
                 }
             }
         }
@@ -549,7 +552,10 @@ impl S3VfsLike {
             .map_err(|e| VfsError::Io(format!("S3 PUT failed: {}", e)))?;
 
         if resp.status() != 200 {
-            return Err(VfsError::Io(format!("PutObject returned {}", resp.status())));
+            return Err(VfsError::Io(format!(
+                "PutObject returned {}",
+                resp.status()
+            )));
         }
         Ok(())
     }
@@ -612,10 +618,7 @@ mod tests {
 
     #[test]
     fn test_path_to_key() {
-        assert_eq!(
-            S3Vfs::path_to_key(Path::new("/foo/bar.txt")),
-            "foo/bar.txt"
-        );
+        assert_eq!(S3Vfs::path_to_key(Path::new("/foo/bar.txt")), "foo/bar.txt");
         assert_eq!(S3Vfs::path_to_key(Path::new("/")), "");
         assert_eq!(
             S3Vfs::path_to_key(Path::new("relative/path")),