feat: stream setup .jsdos bundles on-the-fly instead of duplicating game data

- Add streamSetupBundle() to GameService — reads main bundle as zip,
  replaces config files (.jsdos/dosbox.conf, .jsdos/jsdos.json) with
  setup variants pointing to SETUP.EXE, streams directly to response
- Add GET /api/games/{id}/setup-bundle endpoint that calls the above
- Remove .setup.jsdos disk creation during upload — setupExe is still
  detected and stored in game metadata, but no duplicate bundle is saved
- Update frontend api.js to point setupBundleUrl() to the new endpoint
- Fix pre-existing backslash escaping bug in UploadResource.java path
  normalization (replace('\', '/') instead of replace('\\', '/'))

frontend/src/lib/api.js

@@ -112,5 +112,5 @@ export function bundleUrl(game) {
 /** Get game bundle URL for setup mode (runs SETUP.EXE instead) */
 export function setupBundleUrl(game) {
   if (!game) return null;
-  return `/games/${game.id}.setup.jsdos`;
+  return `/api/games/${game.id}/setup-bundle`;
 }

src/main/java/com/dostalgia/GameResource.java

@@ -103,6 +103,34 @@ public class GameResource {
         }
     }
 
+    /**
+     * Stream a setup .jsdos bundle on-the-fly. No disk duplication —
+     * reads the main bundle and patches config files to point at the
+     * setup executable (SETUP.EXE, INSTALL.EXE, etc.).
+     */
+    @GET
+    @Path("/{id}/setup-bundle")
+    @Produces("application/zip")
+    public Response setupBundle(@PathParam("id") String id) {
+        try {
+            var game = svc.load(id);
+            if (game.getSetupExe() == null || game.getSetupExe().isBlank()) {
+                return Response.status(404)
+                    .entity(Map.of("error", "No setup executable configured for this game"))
+                    .build();
+            }
+            String filename = (game.getTitle() != null ? game.getTitle() : id) + ".setup.jsdos";
+            StreamingOutput stream = output -> svc.streamSetupBundle(id, output);
+            return Response.ok(stream)
+                .header("Content-Disposition", "attachment; filename=\"" + filename + "\"")
+                .build();
+        } catch (NoSuchFileException e) {
+            return Response.status(404).entity(Map.of("error", "Game not found")).build();
+        } catch (Exception e) {
+            return Response.serverError().entity(Map.of("error", e.getMessage())).build();
+        }
+    }
+
     @GET
     @Path("/{id}/download")
     @Produces("application/zip")

src/main/java/com/dostalgia/GameService.java

@@ -10,6 +10,7 @@ import jakarta.enterprise.context.ApplicationScoped;
 import org.eclipse.microprofile.config.inject.ConfigProperty;
 
 import java.io.IOException;
+import java.io.OutputStream;
 import java.nio.file.*;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.time.Instant;
@@ -282,5 +283,45 @@ public class GameService {
         return null;
     }
 
+    /**
+     * Stream a setup .jsdos bundle on-the-fly by reading the main bundle
+     * and replacing config files to point at the setup executable.
+     * No data is written to disk — the modified ZIP is streamed directly.
+     */
+    public void streamSetupBundle(String id, OutputStream out) throws IOException {
+        Game game = load(id);
+        String setupExe = game.getSetupExe();
+        if (setupExe == null || setupExe.isBlank()) {
+            throw new IOException("No setup executable configured for this game");
+        }
+
+        Path bundlePath = gamesDir.resolve(game.getBundleFile());
+        if (!Files.exists(bundlePath)) {
+            throw new NoSuchFileException("Bundle not found: " + game.getBundleFile());
+        }
+
+        byte[] newDosboxConf = buildDosboxConfBytes(setupExe);
+        byte[] newJsdosJson = buildJsdosJsonBytes(setupExe);
+
+        try (var zis = new java.util.zip.ZipInputStream(Files.newInputStream(bundlePath));
+             var zos = new java.util.zip.ZipOutputStream(out)) {
+
+            java.util.zip.ZipEntry entry;
+            while ((entry = zis.getNextEntry()) != null) {
+                String name = entry.getName();
+                zos.putNextEntry(new java.util.zip.ZipEntry(name));
+                if (".jsdos/dosbox.conf".equals(name)) {
+                    zos.write(newDosboxConf);
+                } else if (".jsdos/jsdos.json".equals(name)) {
+                    zos.write(newJsdosJson);
+                } else {
+                    zis.transferTo(zos);
+                }
+                zos.closeEntry();
+                zis.closeEntry();
+            }
+        }
+    }
+
     public Path getGamesDir() { return gamesDir; }
 }

src/main/java/com/dostalgia/UploadResource.java

@@ -103,30 +103,25 @@ public class UploadResource {
             // Detect platform (DOS vs Windows) by reading the main EXE header
             String platform = detectPlatform(Path.of(mainExe));
 
-            // Create setup bundle only if the setup executable is itself DOS-compatible.
+            // Store setup executable path if found and DOS-compatible.
             // Some games (e.g. Fallout) ship a Windows SETUP.EXE even though the main
             // game is DOS — that setup would fail with "This program cannot run in DOS mode".
-            boolean hasSetupBundle = false;
-            if (setupExe != null) {
-                String setupPlatform = detectPlatform(Path.of(setupExe));
-                if (!"windows".equals(setupPlatform)) {
-                    Path setupBundlePath = svc.getGamesDir().resolve(gameId + ".setup.jsdos");
-                    createBundle(extractDir, setupExe, setupBundlePath);
-                    hasSetupBundle = true;
-                }
-            }
+            // The .setup.jsdos bundle is now generated on-the-fly — no disk duplication needed.
 
             // Save metadata
             Game game = new Game(gameId, title);
             game.setBundleFile(bundleFile);
             game.setPlatform(platform);
             // Store the selected executable and the full list for the UI picker
-            String relMain = extractDir.relativize(Path.of(mainExe)).toString().replace('\\', '/');
+            String relMain = extractDir.relativize(Path.of(mainExe)).toString().replace('\', '/');
             game.setExecutable(relMain);
             game.setExecutables(findAllExecutables(extractDir));
-            if (hasSetupBundle) {
+            if (setupExe != null) {
+                String setupPlatform = detectPlatform(Path.of(setupExe));
+                if (!"windows".equals(setupPlatform)) {
                     game.setSetupExe(extractDir.relativize(Path.of(setupExe)).toString());
                 }
+            }
             game.setReady(true);
             svc.save(game);
 
@@ -254,7 +249,7 @@ public class UploadResource {
             public FileVisitResult visitFile(Path f, BasicFileAttributes a) {
                 String name = f.getFileName().toString().toLowerCase();
                 if (name.endsWith(".exe") || name.endsWith(".com") || name.endsWith(".bat")) {
-                    result.add(dir.relativize(f).toString().replace('\\', '/'));
+                    result.add(dir.relativize(f).toString().replace('\', '/'));
                 }
                 return FileVisitResult.CONTINUE;
             }
@@ -433,7 +428,7 @@ public class UploadResource {
             var allDirs = new java.util.TreeSet<String>();
             try (var walk = Files.walk(extractDir)) {
                 walk.filter(Files::isRegularFile).forEach(f -> {
-                    String entryName = extractDir.relativize(f).toString().replace('\\', '/');
+                    String entryName = extractDir.relativize(f).toString().replace('\', '/');
                     int idx = entryName.lastIndexOf('/');
                     while (idx >= 0) {
                         allDirs.add(entryName.substring(0, idx + 1));
@@ -454,7 +449,7 @@ public class UploadResource {
                     .sorted()
                     .forEach(f -> {
                         try {
-                            String entryName = extractDir.relativize(f).toString().replace('\\', '/');
+                            String entryName = extractDir.relativize(f).toString().replace('\', '/');
                             zos.putNextEntry(new java.util.zip.ZipEntry(entryName));
                             Files.copy(f, zos);
                             zos.closeEntry();
@@ -476,7 +471,7 @@ public class UploadResource {
                     .sorted()
                     .forEach(f -> {
                         try {
-                            String entryName = extractDir.relativize(f).toString().replace('\\', '/');
+                            String entryName = extractDir.relativize(f).toString().replace('\', '/');
                             zos.putNextEntry(new java.util.zip.ZipEntry(entryName));
                             Files.copy(f, zos);
                             zos.closeEntry();
@@ -501,7 +496,7 @@ public class UploadResource {
      * If relExe is just a filename, returns {null, relExe}.
      */
     private static String[] splitDirExe(String relExe) {
-        int idx = relExe.replace('\\', '/').lastIndexOf('/');
+        int idx = relExe.replace('\', '/').lastIndexOf('/');
         if (idx >= 0) {
             return new String[]{relExe.substring(0, idx), relExe.substring(idx + 1)};
         }