Phase 0: scaffold Gradle multi-project mod skeleton

common/ (shared source) plus three leaf modules: forge-1_12_2 (primary,
Enigmatica 2 target) and forge-1_7_10 both build via anatawa12's
Gradle-7-compatible ForgeGradle 1.2/2.3 forks (verified: both leaves build
clean on Gradle 7.6 / JDK 8). neoforge-26_1 is structurally scaffolded but
excluded from the default build pending its own toolchain in Phase 10.

neoforge-26_1/src/main/java/com/octoturge/mcmapper/neoforge261/MCMapperMod.java

@@ -0,0 +1,21 @@
+package com.octoturge.mcmapper.neoforge261;
+
+import net.neoforged.bus.api.IEventBus;
+import net.neoforged.fml.common.Mod;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Entry point for the 26.1.2 leaf — lowest MVP priority (Phase 10), stubbed structurally now.
+ * Loader assumed NeoForge; see root plan's Open Assumptions for the verification note.
+ */
+@Mod(MCMapperMod.MOD_ID)
+public class MCMapperMod {
+    public static final String MOD_ID = "mcmapper";
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(MCMapperMod.class);
+
+    public MCMapperMod(IEventBus modEventBus) {
+        LOGGER.info("MCMapper (neoforge-26_1 leaf) scaffolding loaded — no-op until Phase 10");
+    }
+}

neoforge-26_1/src/main/resources/META-INF/neoforge.mods.toml

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+modLoader = "javafml"
+loaderVersion = "[1,)"
+license = "MIT"
+
+[[mods]]
+modId = "mcmapper"
+version = "${file.jarVersion}"
+displayName = "MCMapper"
+description = "Thin delta-streaming client for the MCMapper web map backend."
+authors = "Octoturge"
+
+[[dependencies.mcmapper]]
+    modId = "neoforge"
+    type = "required"
+    versionRange = "[26.1,)"
+    ordering = "NONE"
+    side = "BOTH"