internal: move shim and init into app

This structure makes more sense, as both processes are part of an app's lifecycle.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/init/early.go

@@ -0,0 +1,18 @@
+package init0
+
+import (
+	"os"
+	"path"
+
+	"git.gensokyo.uk/security/fortify/internal/fmsg"
+)
+
+// used by the parent process
+
+// TryArgv0 calls [Main] if argv0 indicates the process is started from a file named "init".
+func TryArgv0() {
+	if len(os.Args) > 0 && path.Base(os.Args[0]) == "init" {
+		Main()
+		fmsg.Exit(0)
+	}
+}