Multiloader scaffold: Architectury common+fabric+forge+neoforge (1.21.1)

Convert the single-loader NeoForge project into an Architectury multiloader:
- root/settings/subproject build.gradle, Gradle pinned to 8.10.2 (Loom needs 8.x)
- common: generic SkinsgCommands<S> + SkinsgClient bootstrap
- per-loader entrypoints (Fabric ClientModInitializer, Forge/NeoForge @Mod) + metadata
- migrate-to-multiloader.sh moves the loader/version-agnostic core into common/
- MULTILOADER.md: build/toolchain/proxy + 1.20.1 switch incl. rewritten cape mixin

main (working NeoForge 1.21.1) untouched.

MULTILOADER.md

@@ -0,0 +1,109 @@
+# skinsg — multiloader / multiversion build guide
+
+Branch `multiloader`. Converts the single-loader NeoForge project into an
+**Architectury** project building **Fabric + Forge + NeoForge** from one codebase.
+MC version is chosen in `gradle.properties` (default **1.21.1**; switch to **1.20.1**
+for the Create To Exile 2 Forge pack — see below).
+
+`main` is untouched (still the working NeoForge 1.21.1 build).
+
+## 0. One-time restructure
+From the repo root on the `multiloader` branch:
+```bash
+bash migrate-to-multiloader.sh
+```
+This `git mv`s the loader/version-agnostic code (`SkinsgConfig`, `gif/`, `client/`,
+`mixin/`, `skinsg.mixins.json`) into `common/`, and removes the old NeoForge entry +
+metadata (recreated per-loader). The new files (already committed on this branch):
+- `common/…/SkinsgClient.java`, `common/…/commands/SkinsgCommands.java` (generic over source type)
+- `fabric|forge|neoforge/…/Skinsg{Fabric,Forge,NeoForge}.java` + their mod metadata.
+
+## 1. Toolchain (important)
+- **Gradle 8.10.2** — wrapper already pinned (Architectury Loom does NOT support Gradle 9).
+- **JDK 21** for 1.21.1 (JDK 17 for 1.20.1). Gradle toolchains auto-pick Liberica 21/17 if installed.
+- **Internet/proxy**: Gradle must reach `maven.architectury.dev`, `maven.fabricmc.net`,
+  `maven.minecraftforge.net`, `maven.neoforged.net`, `maven.parchmentmc.org`. If direct
+  fails on this network, add to `~/.gradle/gradle.properties`:
+  ```
+  systemProp.http.proxyHost=127.0.0.1
+  systemProp.http.proxyPort=1080
+  systemProp.https.proxyHost=127.0.0.1
+  systemProp.https.proxyPort=1080
+  ```
+  (CI already sets the internal `172.21.5.18:1080` proxy.)
+- Plugin versions in root `build.gradle` are `architectury-plugin 3.4-SNAPSHOT` /
+  `dev.architectury.loom 1.7-SNAPSHOT`. If a SNAPSHOT won't resolve, pin the current
+  release from maven.architectury.dev (e.g. loom `1.7.4`, plugin `3.4.159`).
+
+## 2. Build
+```bash
+./gradlew build
+```
+Output jars (the ones WITHOUT a classifier):
+- `fabric/build/libs/skinsg-fabric-0.1.0.jar`
+- `forge/build/libs/skinsg-forge-0.1.0.jar`
+- `neoforge/build/libs/skinsg-neoforge-0.1.0.jar`
+
+Dev test: `./gradlew :neoforge:runClient` (or `:fabric:`, `:forge:`).
+
+## 3. Switch to 1.20.1 (what CtE2 needs: Forge 1.20.1)
+CtE2 = Forge **1.20.1-47.4.10**. Do this on a `multiloader-1.20.1` branch (or flip props):
+
+### a) `gradle.properties`
+```
+minecraft_version=1.20.1
+minecraft_version_range=[1.20.1]
+parchment_minecraft=1.20.1
+parchment_version=2023.09.03
+architectury_api_version=9.2.14
+fabric_loader_version=0.16.9
+fabric_api_version=0.92.5+1.20.1
+forge_version=1.20.1-47.4.10
+neoforge_version=47.1.106     # 1.20.1 NeoForge (only if you build the neoforge target too)
+```
+### b) mixins: JAVA_17
+In `common/…/resources/skinsg.mixins.json` set `"compatibilityLevel": "JAVA_17"`.
+
+### c) metadata version ranges → `[1.20,1.21)`, and `java >=17` in fabric.mod.json,
+`loaderVersion="[47,)"` + `forge`/`minecraft` ranges in `forge/…/mods.toml`.
+
+### d) CapeMagicMixin — **rewrite** (1.20.1 has no `PlayerSkin`)
+1.20.1 exposes the cape as a `ResourceLocation`, so target `getCloakTextureLocation`
+instead of `getSkin`. Replace `common/…/mixin/CapeMagicMixin.java` with:
+```java
+package xyz.nightsync.skinsg.mixin;
+
+import com.mojang.authlib.GameProfile;
+import net.minecraft.client.player.AbstractClientPlayer;
+import net.minecraft.resources.ResourceLocation;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+import xyz.nightsync.skinsg.client.CapeManager;
+
+@Mixin(AbstractClientPlayer.class)
+public abstract class CapeMagicMixin {
+    @Inject(method = "getCloakTextureLocation", at = @At("RETURN"), cancellable = true)
+    private void skinsg$overrideCape(CallbackInfoReturnable<ResourceLocation> cir) {
+        GameProfile profile = ((AbstractClientPlayer) (Object) this).getGameProfile();
+        ResourceLocation animated = CapeManager.getCape(profile.getId());
+        if (animated != null) cir.setReturnValue(animated);
+    }
+}
+```
+`SkinMagicMixin` (HttpTexture.processLegacySkin) targets the same method on 1.20.1 —
+should compile unchanged; verify the two `@Shadow` helper names still exist in 1.20.1 mappings.
+
+### e) CapeManager — one line
+`ResourceLocation.fromNamespaceAndPath(MODID, ...)` (1.21 only) → `new ResourceLocation(MODID, ...)` on 1.20.1.
+
+### f) build → `forge/build/libs/skinsg-forge-0.1.0.jar` → drop into
+`/srv/nightsyncweb/launcher/data/updates/CreateToExile2/mods/` (remove the current
+NeoForge jar first), then on .12: `glperms sync`.
+
+## Known TODO / verify-in-game (this is the part only you can confirm)
+- Mixin targets/`@Shadow` names against the actual 1.20.1 vs 1.21.1 Mojmap+Parchment mappings.
+- Forge 1.21.1 (52.x) `TickEvent.ClientTickEvent` import path (kept the 1.20/1.21 Forge API).
+- Architectury/Loom exact plugin+API versions (bump if resolve fails).
+- Actual cape/skin rendering — launch each target and look.