Port Create to Minecraft 26.2

[doscarchase]

Summary

• Port Create to Minecraft 26.2 / NeoForge 26.2.0.8-beta.
• Move Java toolchain and CI/Jenkins config from 21 to 25.
• Update Gradle wrapper to 9.6.1 and disable Parchment until 26.2 mappings are available.
• Update required dependency coordinates for the 26.2 Registrate, Flywheel, Vanillin, and Ponder release train.
• Gate Maven-local repository usage behind create.useMavenLocal so the default PR path resolves published coordinates only.
• Update supported optional integrations with available 26.2 artifacts: JEI 30.7.0.40, Sodium mc26.2-0.9.1-beta.4-neoforge, and CC: Tweaked 1.120.1.
• Gate optional integrations without 26.2 builds: Curios, Farmer's Delight, FTB, JourneyMap, and Xaero.
• Retarget registries, recipes, generated data, data components, tags, mixins, rendering bridges, fluids/items adapters, networking payloads, and game tests to 26.2 APIs.
• Move avoidable client-only references behind client-side classes/services so the dedicated server reaches startup.
• Update pack.mcmeta to resource major 88 and data format 107.1.

Maintainer Note

• The release plan calls for upstream mc26.2/dev to be created from mc1.21.1/dev before merge.
• This account cannot create upstream branches (403), so this PR is opened against mc1.21.1/dev and should be retargeted to mc26.2/dev after maintainers create it.
• Required dependency artifacts are still pending official publication.

Dependency PRs / Releases

• Registrate 26.2: pending official publish.
• Flywheel/Vanillin 26.2: pending official publish.
• Ponder/Catnip 26.2: pending official publish after Flywheel.

Validation

• ./gradlew "-Pcreate.useMavenLocal" --offline clean build --stacktrace --no-daemon --console=plain -> BUILD SUCCESSFUL in 49s
• ./gradlew "-Pcreate.useMavenLocal" --offline runData --stacktrace --no-daemon --console=plain -> BUILD SUCCESSFUL in 44s
• runData cache summary: total files: 7499, old count: 7499, new count: 7499, removed stale: 0, written: 0
• ./gradlew "-Pcreate.useMavenLocal" --offline runGameTestServer --stacktrace --no-daemon --console=plain -> All 1 required tests passed :), BUILD SUCCESSFUL in 37s
• ./gradlew -Pcreate.useMavenLocal --offline runServer --stacktrace --no-daemon --console=plain -> dedicated server reached Done (0.320s)! For help, type "help"; harness stopped the validation JVM after startup.
• ./gradlew -Pcreate.useMavenLocal --offline runClient --stacktrace --no-daemon --console=plain -> client bootstrap reached Sound engine started and created blocks/items/gui texture atlases; harness stopped the validation JVM after startup markers.

Runtime Smoke

• Automated server-side game test server startup and test execution passed locally.
• Dedicated server startup passed locally with no LocalPlayer, DISTXFORM, or unresolved Ponder/Catnip version-difference warnings.
• Automated client bootstrap passed locally with no Flywheel RGBA/LUMINANCE resource reload error.
• Full manual client main-menu confirmation, fresh-world load, core Create system smoke coverage, JEI category inspection, Flywheel rendering inspection, Ponder scene inspection, and 1.21.1-world migration checks still need maintainer runtime signoff before merge.

Deferred Optional Integrations

• Curios
• Farmer's Delight
• FTB
• JourneyMap
• Xaero

[TropheusJ]

Regardless of the actual quality of this code, this PR is unmergeable. Nearly 40k lines of changes, in a single commit, is not possible to review.