Fix legacy Codec compatibility on Forge 1.12.2

[SkyBlade1978]

Summary

• fix issue Crash with Cleanroom 0.6.12 (Client only) #298 by removing OreSpawn's startup-time direct linkage to the class-shaped legacy com.mojang.serialization.Codec adapter
• add an internal class/interface-neutral bridge that supports both OreSpawn's bundled adapter and an interface-shaped Codec supplied earlier on a legacy modpack classpath
• preserve StandardPatternSettings.CODEC, OrePatternType.create(Codec, Function), OrePatternType.codec(), API major 1, schemas 4/6/5, profiles, migrations, registries, and world-generation behavior
• update the changelog, README, version documentation, reports, Maven identity, workflows, and artifacts to 4.0.17.112021
• ensure every automated and generated Eclipse server launch uses Forge 1.12's literal trailing nogui argument and rejects --nogui

This is deliberately a Forge 1.12.2 compatibility release. Cleanroom targets Minecraft 1.12.2, and no other OreSpawn branch will receive the bridge without target-native evidence of the same class/interface collision.

Validation

• reporter confirmed the supplied 4.0.17.112021 candidate boots their Cleanroom client and connects to their server
• 158 JUnit tests across 39 suites; zero failures, errors, or skips
• hermetic interface-first reproduction fails on exact 4.0.16 with the reported IncompatibleClassChangeError and passes on 4.0.17
• unchanged API consumer compiled against 4.0.16 registers and decodes successfully
• complete Java 17/Temurin 8 offline lifecycle passed in the main checkout and a cold exact-commit worktree
• all three public jars were byte-identical between main and cold builds
• empty Gradle-home Forge bootstrap passed with official MinecraftMavenizer 0.5.19 and no compatibility patch; same-cache offline replay passed
• exact reobfuscated Forge 14 packaged server fresh/reload passed with bare nogui
• Cleanroom 0.6.12 interface-first fresh/reload server controls passed with the fixture verified as the winning Codec source
• 39 runtime logs scanned with zero IncompatibleClassChangeError, NoSuchMethodError, AbstractMethodError, or ClassCastException; zero crash reports or surviving test processes
• artifact audit retained Java 8 class major 52, Forge 14 metadata, FMLAT, both access-transformer rules, documentation/locales, and zero fixture/test/world leakage

Exact main jar SHA-256: DA99AC45B663E0FB582AC175E7D5AC53C962BD03F00E79299C4BE0E33E9DCCF2

Addresses #298.