fix: suppress console window for stdio MCP servers in release builds

The gateway's StdioTransport was missing the CREATE_NO_WINDOW flag when
spawning child processes. In release builds, the Tauri app uses
windows_subsystem = "windows" (GUI subsystem), which causes Windows to
allocate a new visible console for each spawned console-subsystem child
process. This adds the same CREATE_NO_WINDOW (0x08000000) creation flag
already used in the mcpmux-mcp crate's transport.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Mohammod Al Amin Ashik <maa.ashik00@gmail.com>

Author: its-mash

crates/mcpmux-gateway/src/pool/transport/stdio.rs

@@ -125,6 +125,16 @@ impl Transport for StdioTransport {
                     .stderr(Stdio::piped()) // Capture stderr for logging
                     .kill_on_drop(true);
 
+                // On Windows, prevent console window from appearing for child processes.
+                // In release builds the app uses `windows_subsystem = "windows"` (GUI subsystem),
+                // which causes Windows to allocate a new visible console for any spawned
+                // console-subsystem child process. CREATE_NO_WINDOW suppresses this.
+                #[cfg(windows)]
+                {
+                    const CREATE_NO_WINDOW: u32 = 0x08000000;
+                    cmd.creation_flags(CREATE_NO_WINDOW);
+                }
+
                 // Note: We can't easily access stderr after TokioChildProcess wraps it
                 // This is a limitation of the current rmcp API
                 // For now, we log connection events only