Implement plugin catalog and discovery system

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

internal/plugin/exec_windows.go

@@ -0,0 +1,42 @@
+//go:build windows
+
+/*
+Copyright 2026 The Flux authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package plugin
+
+import (
+	"os"
+	"os/exec"
+)
+
+// Exec runs the plugin as a child process with full I/O passthrough.
+// Matches kubectl's Windows fallback pattern.
+func Exec(path string, args []string) error {
+	cmd := exec.Command(path, args...)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.Env = os.Environ()
+	err := cmd.Run()
+	if err == nil {
+		os.Exit(0)
+	}
+	if exitErr, ok := err.(*exec.ExitError); ok {
+		os.Exit(exitErr.ExitCode())
+	}
+	return err
+}