JDK_HOME can be sorted after lower-priority auto-detected JDK sources

[shblue21]

Describe the bug
When java.jdt.ls.java.home and java.home are unset, a JDK from JDK_HOME can be sorted after JDKs detected from JAVA_HOME, PATH, or other sources.

JDK_HOME should be the top-priority environment variable in this case.

To Reproduce

1. Leave java.jdt.ls.java.home, java.home, and java.configuration.runtimes unset.
2. Ensure java.configuration.detectJdksAtStart is enabled.
3. Set JDK_HOME to a valid JDK.
4. Make a different valid JDK available through JAVA_HOME or PATH.
5. Restart VS Code.
6. Open Java: Configure Java Runtime and check the detected JDK order.

Actual behavior
The JDK_HOME JDK can appear after lower-priority detected JDKs.

Expected behavior
The JDK_HOME JDK appears first.

Environment

• Operating System: macOS
• JDK version: JDK 17 from JDK_HOME, JDK 25 from JAVA_HOME
• Visual Studio Code version: 1.125.0-insider
• Java extension version: 1.55.0

Additional Information
sortJdksBySource() assigns JDK_HOME rank 0, but the later if (jdk.rank) check skips it because 0 is falsy.