feat(java): Separate the jdtls JDK and add Settings for New Projects (#21)

- Languages & Frameworks › Java › Language Server › JDK (languages.java.jdtlsJdk) runs jdtls on its own JDK, like IDEA's JDK for importer; the project keeps compiling and running with the Project JDK.
- Toolchain pages get the Global / This project switch (default This project); Global shows and edits the global layer.
- File › New Projects Setup › Settings for New Projects… edits only the global layer, which new projects inherit.
- Configuration errors (launch_error) show as "Not started" instead of "Crashed".

Fixes #18
Fixes #19

Claude-Session: https://claude.ai/code/session_01SaPPsVPuk6ZTNsoUCNCbMv

src/features/code-insight/views.test.ts

@@ -44,6 +44,7 @@ describe("serversSummary", () => {
     expect(serversSummary([s("rust-analyzer", "ready")])).toEqual({ text: "rust-analyzer", tone: "ok" });
     expect(serversSummary([s("vtsls", "ready"), s("eslint", "starting")])).toEqual({ text: "vtsls +1", tone: "busy" });
     expect(serversSummary([s("gopls", "missing")])!.tone).toBe("error");
+    expect(serversSummary([s("jdtls", "misconfigured")])!.tone).toBe("error");
   });
 });