Use Forge context for Cleanroom CurseForge files (#4337)

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

docs/mods-and-plugins/curseforge-files.md

@@ -4,6 +4,8 @@ Mods and plugins can be auto-downloaded and upgraded from CurseForge by setting
 
 A specific file can be omitted from each reference to allow for auto-selecting the newest version of the selected mod/plugin. The resolved `VERSION` and `TYPE` will be taken into consideration for selecting the appropriate file. 
 
+When `TYPE` is `CLEANROOM`, `CURSEFORGE_FILES` uses the Forge loader context to select compatible files. This only affects CurseForge file resolution; the server still runs with Cleanroom.
+
 !!! info "CurseForge API key usage"
 
     A CurseForge API key is _now_ included by this image on Java 17 and newer; however, you can always supply your own instead. A CurseForge API key can be allocated and set with `CF_API_KEY` (or `CF_API_KEY_FILE`) [as described here](../types-and-platforms/mod-platforms/auto-curseforge.md#api-key). The `java8` image (and other pre-Java 17 tags) does not include a baked-in key; set `CF_API_KEY` yourself.

scripts/start-setupModpack

@@ -342,6 +342,9 @@ function handleCurseForgeFiles() {
     forge|neoforge|fabric|quilt)
       args+=(--mod-loader "$TYPE")
       ;;
+    cleanroom)
+      args+=(--mod-loader forge)
+      ;;
     *)
       if isFamily HYBRID; then
         # To disambiguate mc-mods we'll assume that hybrid servers