feat: setup dynamic passphrase in level

level/example/hello-world/Dockerfile

@@ -1,2 +1,3 @@
 FROM nginx
-COPY static /usr/share/nginx/html
+COPY static /usr/share/nginx/html
+COPY on-init /pathwar-hooks/

level/example/hello-world/on-init

@@ -0,0 +1,3 @@
+#!/bin/sh -e
+
+sed -i "s/THE_PASSPHRASE/$(pwctl passphrase 0)/g" /usr/share/nginx/html/index.html

level/example/hello-world/static/index.html

@@ -1 +1,3 @@
 <h1>Hello World!</h1>
+
+<p>Here is a dynamic passphrase: <b>THE_PASSPHRASE</b></p>

pwctl/main.go

@@ -23,10 +23,18 @@ func main() {
 	rootCmd.AddCommand(&cobra.Command{
 		Use:  "entrypoint",
 		Args: cobra.MinimumNArgs(1),
-		RunE: func(cmd *cobra.Command, args []string) error {
-			// FIXME: prepare the level
-			// FIXME: add a self-destruct mode that allow having root access only at runtime
+		RunE: func(_ *cobra.Command, args []string) error {
 			// FIXME: lock to block other commands
+
+			// prepare the level
+			cmd := exec.Command("/pathwar-hooks/on-init")
+			if err := cmd.Run(); err != nil {
+				return err
+			}
+
+			// FIXME: add a self-destruct mode that allow having root access only at runtime
+
+			// switch to original's entrypoint
 			binary, err := exec.LookPath(args[0])
 			if err != nil {
 				return err