docs(buf): fix for IoBufferMut::len

Co-authored-by: Copilot <[email protected]>

compio-buf/src/io_buffer.rs

@@ -142,7 +142,7 @@ impl IoBufferMut {
         self.ptr
     }
 
-    /// Get the initialized length of the buffer.
+    /// Get the total length of the buffer (may include both initialized and uninitialized bytes).
     pub fn len(&self) -> usize {
         self.len
     }