fix: add illumos/solaris support for disk space check (#798)

Solaris/illumos use Statvfs (POSIX standard) rather than Statfs.
Add daemon_health_solaris.go and exclude illumos/solaris from the
generic unix build constraint.

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/daemon_health_solaris.go

@@ -0,0 +1,23 @@
+//go:build illumos || solaris
+
+package main
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// checkDiskSpace returns the available disk space in MB for the given path.
+// Returns (availableMB, true) on success, (0, false) on failure.
+func checkDiskSpace(path string) (uint64, bool) {
+	var stat unix.Statvfs_t
+	if err := unix.Statvfs(path, &stat); err != nil {
+		return 0, false
+	}
+
+	// Calculate available space in bytes, then convert to MB.
+	// On Solaris/illumos, Frsize is the fragment size (fundamental block size).
+	availableBytes := stat.Bavail * stat.Frsize
+	availableMB := availableBytes / (1024 * 1024)
+
+	return availableMB, true
+}

cmd/bd/daemon_health_unix.go

@@ -1,4 +1,4 @@
-//go:build !windows && !wasm && !freebsd
+//go:build !windows && !wasm && !freebsd && !illumos && !solaris
 
 package main