fix: suppress windows during headless test execution

- Launcher: use SW_HIDE for WA.exe window when OPENWA_HEADLESS=1 is set
- Test runner: use CREATE_NO_WINDOW when spawning launcher processes

Eliminates console windows and most WA windows during test runs.
The brief "Loading" dialog still flashes — hooking ShowWindow causes
WA to throttle (minimized) or hang (hidden), so it's left as-is.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/openwa-launcher/src/main.rs

@@ -53,6 +53,7 @@ struct PROCESS_INFORMATION {
 
 const CREATE_SUSPENDED: DWORD = 0x0000_0004;
 const STARTF_USESHOWWINDOW: DWORD = 0x0000_0001;
+const SW_HIDE: u16 = 0;
 const SW_SHOWMINIMIZED: u16 = 2;
 const INFINITE: DWORD = 0xFFFF_FFFF;
 

crates/openwa-test-runner/src/main.rs

@@ -7,12 +7,15 @@
 use std::env;
 use std::fmt::Write as FmtWrite;
 use std::fs;
+use std::os::windows::process::CommandExt;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::sync::mpsc;
 use std::thread;
 use std::time::{Duration, Instant};
 
+const CREATE_NO_WINDOW: u32 = 0x0800_0000;
+
 // ─── Configuration ──────────────────────────────────────────────────────────
 
 const DEFAULT_JOBS: usize = 4;
@@ -223,6 +226,7 @@ fn run_test(test: &TestCase, launcher: &Path, wa_exe: &Path, run_dir: &Path) ->
         .env("OPENWA_LOG_PATH", &openwa_log)
         .stdout(std::process::Stdio::null())
         .stderr(std::process::Stdio::null())
+        .creation_flags(CREATE_NO_WINDOW)
         .status();