Port OreSpawn 4.0.16 to Forge 1.21.1

[SkyBlade1978]

Summary

Ports the complete OreSpawn 4.0.16 campaign to Minecraft 1.21.1 / Forge 52.1.0 and updates the target identity to 4.0.16.121011.

This carries the accepted fixes for:

• long Ore and Fluid editor values surviving open/save cycles;
• provider-declared natural terrain replacement ordering and unsafe-source protection (Residual vanilla Dirt survives total-conversion terrain replacement #255);
• Stable Layers rock bounds using actual world Y;
• dynamic biome registry weights and managed-ore filters ([1.18.2] Geome ID fallback drops biome-dictionary weights for dynamic biomes #262 and [1.18.2] Ore biome filters reject dynamic-registry biomes by object identity #263);
• public sampler height alignment ([1.18.2] GeologySampler disagrees with generated geology at 3D biome seams #266);
• provider biome-filter API parity and namespaced geome IDs ([1.18.2 API] OreDimensionDefinition.Builder cannot express supported biome filters #268 and [1.18.2] Creation editor rejects namespaced geome IDs in valid templates #269);
• exposed one-layer Snow and surface Ice conversion ([1.18.2] Dimension snow/ice material overrides do not convert loaded weather blocks #267);
• stable direct biome attribution shared by generation, sampling, and family-restricted ores;
• GameTest benchmark shutdown ownership.

It also moves the branch to ForgeGradle 7.0.34 / Gradle 9.6.1, retains Java 21 and official Forge 52 runtime naming, adds reproducible release artifacts and cold-bootstrap validation, and updates the README, changelog, version policy, documentation export, workflows, and Maven identity.

API major 1, schemas 4/6/5, registry IDs, existing provider fields, migrations, profiles, and existing chunks remain compatible.

Validation

• 134 tests across 33 suites, with no failures, errors, or skips.
• 40 JSON/mcmeta files parsed; 16 locales with 359 matching keys; all 21 documents exported in parity.
• Full offline build, Javadocs, artifact audit, checksums, Buildship runs, and production Eclipse classpath checks passed.
• A cold exact-commit worktree reproduced all three release jars byte-for-byte.
• Empty-cache Forge 52 bootstrap used Java 25 and correctly required zero target compatibility patches; same-cache offline rerun passed.
• Exact official-named Forge 52 packaged server fresh/reload and packaged client create/render/save/reload/editor tests passed with clean logs.
• Surface, natural-host, dynamic-biome, weather-material, fluid, sentinel, stable-attribution, preferred-seed, and benchmark lifecycle gates passed fresh and reload.
• Three matched 81-chunk repetitions measured Sky at 35.791 ms/chunk, Cyano at 49.164, and vanilla at 45.597; no regression was found.
• The exact candidate was manually tested and accepted before publication to the fork.

No direct MMD branch update, tag, or release is included in this PR.