Allow releases from all Minecraft target branches

[SkyBlade1978]

The release action found the 1.13 branch correctly, then rejected it because a later check only allowed 1.12 and 1.18. This removes that restriction and uses each target branch's release metadata instead.

• Support OreSpawn's Forge and NeoForge branch naming, including 26.x targets, without adding a new allowlist entry for every port.
• Keep the pinned Java 17 Gradle runtime for legacy ports and validate the game and Gradle Java selectors separately.
• Read the required OreSpawn relation from modern port metadata without adding MMDLib. The 1.12 release still requires both mods.
• Clean NeoForge builds separately, matching OreSpawn's release workflow.
• Keep the repository, version, prior-CI, tag, checksum and publication-confirmation guards in place.

Added tests which run the workflow's actual Bash with local GitHub stubs. The unchanged workflow failed for 1.13; the corrected workflow passes the Forge/NeoForge target matrix and rejection tests. All 42 local tests, check/build/Javadoc, release artifact auditing and actionlint pass. No gameplay code has changed.

The release guide explains how future target branches supply their metadata and verified dependency staging.