Upgrade Java toolchain to JDK 25

[henrist]

Summary

This PR upgrades the project's Java toolchain from JDK 21 to JDK 25 and configures Renovate to automatically track Java version updates across the codebase.

Key Changes

• Build configuration: Updated jvmToolchain in build.gradle.kts from 21 to 25
• CI/CD: Updated Java version in GitHub Actions workflow from 21 to 25
• Documentation: Updated minimum JDK requirement in CLAUDE.md from 21+ to 25+
• Renovate configuration: Added custom managers to automatically detect and update Java versions in:
  • build.gradle.kts files (via jvmToolchain() calls)
  • GitHub Actions workflow files (via java-version property)
• Package grouping: Configured Renovate to group Java-related dependencies (eclipse-temurin, java) under a "jdk" group for consolidated updates

Implementation Details

The Renovate custom managers use regex patterns to extract Java version numbers from both Gradle and GitHub Actions configurations, enabling automated dependency updates while maintaining consistency across the project.

https://claude.ai/code/session_019kXZo4xkVeDx3t1uqKnxiC

Summary by CodeRabbit

• Chores
  • Updated Java/JDK toolchain requirement from version 21 to 25 across build configuration, CI/CD pipeline, and project documentation
  • Configured automated dependency management system for Java packages to enable efficient tracking and updates of the development toolchain

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR updates the Java toolchain version from 21 to 25 across CI workflow, build configuration, and documentation files. Additionally, Renovate configuration is enhanced with custom managers to automatically extract and group Java/JDK dependency updates.

Changes

Cohort / File(s)	Summary
Java Version Updates .github/workflows/ci.yml, CLAUDE.md, build.gradle.kts	Updated Java toolchain version from 21 to 25 in CI workflow, build configuration, and documentation.
Renovate Configuration renovate.json	Added custom managers with regex patterns to extract Java versions from build.gradle.kts and GitHub workflow files. Introduced packageRules grouping Java/JDK packages under "jdk" group.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 From twenty-one to twenty-five we hop,
New Java tools make builds go non-stop,
Renovate learns to track and compile,
Dependencies grouped with DevOps style!
The warren's toolchain now stands quite tall! 🛠️

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change in the pull request: upgrading the Java toolchain from JDK 21 to JDK 25 across build configuration, CI/CD, and documentation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into master

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch claude/update-jdk-lts-Mpa9D

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No actionable comments were generated in the recent review. 🎉

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