fix(forge): correct mods.toml dependency schema and mixin refmap name

Two bugs made the built forge jar unusable in a Forge 1.20.1 production
client:

- mods.toml used the NeoForge dependency schema (type = "required")
  instead of Forge's mandatory = true. Forge threw
  InvalidModFileException during the mods-folder scan, which aborts
  discovery of the ENTIRE folder -> the whole modpack failed to load
  (only Minecraft+FML showed). architectury set mandatory = false since
  the code doesn't actually use it.

- skinsg.mixins.json referenced refmap "skinsg.refmap.json" but Loom
  bundles it as "skinsg-common-common-refmap.json". With no refmap
  loaded, CapeMagicMixin's @Inject on getCloakTextureLocation could not
  be remapped to its SRG name -> InvalidInjectionException -> hard crash.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

common/src/main/resources/skinsg.mixins.json

@@ -3,7 +3,7 @@
   "minVersion": "0.8",
   "compatibilityLevel": "JAVA_17",
   "package": "xyz.nightsync.skinsg.mixin",
-  "refmap": "skinsg.refmap.json",
+  "refmap": "skinsg-common-common-refmap.json",
   "client": [
     "SkinMagicMixin",
     "CapeMagicMixin"

forge/src/main/resources/META-INF/mods.toml

@@ -11,21 +11,21 @@ description = '''Client-side HD skins (up to 2048) and animated GIF cape support
 
 [[dependencies.skinsg]]
 modId = "forge"
-type = "required"
+mandatory = true
 versionRange = "[47,)"
 ordering = "NONE"
 side = "CLIENT"
 
 [[dependencies.skinsg]]
 modId = "minecraft"
-type = "required"
+mandatory = true
 versionRange = "[1.20.1,1.21)"
 ordering = "NONE"
 side = "CLIENT"
 
 [[dependencies.skinsg]]
 modId = "architectury"
-type = "required"
+mandatory = false
 versionRange = "[9.2.14,)"
 ordering = "AFTER"
 side = "CLIENT"