Add Java extension support and configure multiple JDK runtimes.
Introduce a wrapped VS Code package that includes JDK 25 in the PATH
to support the Red Hat Java language server.
Switch from using `programs.vscode.userSettings` to a manually managed
`settings.json` file via `home.file`. This allows the settings file to
be writable by external tools like `kilo-code` at runtime while
preserving them across Nix configuration switches by using `force = false`.
Olivier
86dc80eb3c