## Issue
The Dev Container had drifted from the project's CI setup: it pinned the
Oracle JDK distribution at version 21, while CI builds use **Temurin**
across JDK 17/21/25, with the release and docs builds running on **JDK
25**.
## Change
Modernize `.devcontainer/devcontainer.json` to align with CI and add
sensible defaults:
- **JDK distribution**: `oracle` → `tem` (Temurin), matching CI.
- **JDK version**: `21-oracle` → `25`, matching the release/docs builds.
(The project still keeps Java 17 source compatibility.)
- **Maven**: now installed via the Java feature (`installMaven: true`).
- **VS Code settings**: `java.configuration.updateBuildConfiguration:
automatic` and `java.compile.nullAnalysis.mode: automatic` for a
smoother experience on this large multi-module project.
- **Extensions**: added `redhat.vscode-yaml` (workflows) and
`editorconfig.editorconfig` (the repo ships an `.editorconfig`).
- **postCreateCommand**: `java -version && mvn -version` to verify the
toolchain on create.
- Renamed the container display name from "Java" to "LangChain4j".
The existing `azure-cli`, `docker-in-docker`, and `github-cli` features
are kept unchanged.
## General checklist
- [x] There are no breaking changes
- [x] I have manually run all the unit and integration tests in the
module I have added or changed, and they are all green
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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