fix(windows): CREATE_BREAKAWAY_FROM_JOB to survive PowerShell pipelines

PowerShell uses Windows Job Objects to manage pipeline processes. When the
launcher exits, the Job Object kills all child processes — including the
daemon that was just spawned — forcing a full cold restart on every command.

Add CREATE_BREAKAWAY_FROM_JOB (0x01000000) to the daemon's CreationFlags so
it is detached from the parent Job Object and survives launcher exit.

Without this fix: daemon killed after every invocation from PowerShell,
hot-path took 4-15s due to repeated cold restarts.
With this fix: daemon persists across launcher exits, hot-path ~600ms.

Git Bash was unaffected because it does not use Job Objects for child
process tracking.

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

Author: engalar

cmd/mxcli-launcher/spawn_windows.go

@@ -9,8 +9,19 @@ import (
 	"syscall"
 )
 
-// hideDaemonWindow prevents a console window from flashing when the daemon
-// process is started in the background on Windows.
+const (
+	// createBreakawayFromJob detaches the child process from the parent's
+	// Job Object. Without this flag, PowerShell pipelines (which use Job
+	// Objects) kill all child processes when the launcher exits — causing
+	// the daemon to be killed on every invocation and forcing cold restarts.
+	createBreakawayFromJob = 0x01000000
+)
+
+// hideDaemonWindow hides the console window and detaches the daemon from the
+// launcher's Job Object so it survives across PowerShell pipeline boundaries.
 func hideDaemonWindow(cmd *exec.Cmd) {
-	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		HideWindow:    true,
+		CreationFlags: createBreakawayFromJob,
+	}
 }