build: update GitHub Actions to latest major versions

[kikoso]

Description

This PR updates all GitHub Action workflows to their latest stable major versions as of May 2026. These updates ensure compatibility with the Node.js 24 runtime and modern CI/CD standards.

Changes

• actions/checkout: Upgraded to v6.
• actions/setup-java: Upgraded to v5. Migrated distribution: 'adopt' to 'temurin' (AdoptOpenJDK is deprecated).
• actions/setup-python: Upgraded to v6.
• gradle/actions/setup-gradle: Upgraded to v6.
• github/codeql-action/upload-sarif: Upgraded to v4.
• peter-evans/create-pull-request: Upgraded to v8.
• googleapis/release-please-action: Upgraded to v5.

Integrity & Path Validation

• Verified that all SARIF report paths in lint.yml correctly map to the subproject build directories defined in settings.gradle.kts.
• Confirmed that no upload-artifact name collisions exist (v7 immutable backend requirement).
• Surgical updates were applied to maintain existing build and test logic.