Add pure process-path to class normalization for Windows

internal/winapi/class.go

@@ -0,0 +1,21 @@
+// Package winapi is the Windows Win32 binding layer for AntiDrift's OS ports.
+// The syscall-bound code lives in windows-tagged files; this untagged file
+// holds the pure path logic so it builds and is tested on every platform.
+package winapi
+
+import "strings"
+
+// ClassFromImagePath derives the on-task class identity from a process image
+// path: the base file name with any trailing ".exe" removed (case-insensitive),
+// lowercased. It is the Windows analog of an X11 WM_CLASS. It parses both `\`
+// and `/` separators so it is correct regardless of the host OS running the
+// test. Returns "" for an empty path.
+func ClassFromImagePath(p string) string {
+	if i := strings.LastIndexAny(p, `\/`); i >= 0 {
+		p = p[i+1:]
+	}
+	if len(p) >= 4 && strings.EqualFold(p[len(p)-4:], ".exe") {
+		p = p[:len(p)-4]
+	}
+	return strings.ToLower(p)
+}

internal/winapi/class_test.go

@@ -0,0 +1,21 @@
+package winapi
+
+import "testing"
+
+func TestClassFromImagePath(t *testing.T) {
+	cases := []struct{ in, want string }{
+		{`C:\Program Files\Microsoft VS Code\Code.exe`, "code"},
+		{`C:\Windows\explorer.exe`, "explorer"},
+		{`chrome.exe`, "chrome"},
+		{`C:\x\FOO.EXE`, "foo"},
+		{`C:\x\My.App.exe`, "my.app"},
+		{`C:/forward/slash/Code.exe`, "code"},
+		{`firefox`, "firefox"},
+		{``, ""},
+	}
+	for _, c := range cases {
+		if got := ClassFromImagePath(c.in); got != c.want {
+			t.Errorf("ClassFromImagePath(%q) = %q, want %q", c.in, got, c.want)
+		}
+	}
+}