DownloadChecksumJob fails for Gradle snapshot versions fetched from versions API, causing projects to fall back to unmanaged/invisible project mode #4357

Description:

Extension version: redhat.java 1.53.0
OS: Linux (Ubuntu 24)
Java version: (openjdk version "11.0.30" 2026-01-20)
Gradle versions in projects: 6.4, 6.5, 6.8, 7.6.3, 8.3, 8.4 (none using 9.3.0)

Problem:
On every startup, DownloadChecksumJob attempts to validate a checksum for gradle-9.3.0-20251002004537+0000 — a snapshot version not used by any project in the workspace. The snapshot URL no longer exists on Gradle's distribution server, causing a FileNotFoundException. This causes Buildship to fail importing affected projects as Gradle projects, falling back to unmanaged/invisible project mode and outputting compiled classes to bin/ instead of build/.
Evidence:

No project in the workspace references 9.3.0
The version appears in workspaceStorage/.../org.eclipse.buildship.core/gradle/versions.json, suggesting Buildship fetches all versions from the Gradle versions API (including snapshots) and attempts checksum validation for all of them
Deleting the workspaceStorage folder is only a temporary fix as it regenerates on next startup

Expected behavior:
Checksum validation should only run for Gradle versions actually used by projects in the workspace, not all versions fetched from the remote API.