feat(wisdom): enhance vscode module with java support and writable settings

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`.

modules/wisdom/editors/vscode.nix

@@ -12,8 +12,23 @@
         jnoortheen.nix-ide
         yzhang.markdown-all-in-one
         esbenp.prettier-vscode
+        vscjava.vscode-java-pack
+        redhat.java
       ];
 
+      # Wrap VS Code so a JDK is on PATH — the Red Hat Java language server (and
+      # other extension-bundled JVMs) need `java` to run, independent of the
+      # per-project `java.configuration.runtimes` setting.
+      vscodeWithJdk = pkgs.symlinkJoin {
+        name = "vscode-with-jdk";
+        paths = [ pkgs.vscode ];
+        nativeBuildInputs = [ pkgs.makeWrapper ];
+        postBuild = ''
+          wrapProgram "$out/bin/code" \
+            --prefix PATH : "${pkgs.jdk25}/bin"
+        '';
+      };
+
       coreSettings = {
         "nix.enableLanguageServer" = true;
         "nix.serverPath" = "nixd";
@@ -26,7 +41,26 @@
         };
         "diffEditor.ignoreTrimWhitespace" = false;
         "chat.disableAIFeatures" = true;
+
+        "java.configuration.runtimes" = [
+          {
+            name = "JavaSE-21";
+            path = "${pkgs.jdk21}/lib/openjdk";
+          }
+          {
+            name = "JavaSE-25";
+            path = "${pkgs.jdk25}/lib/openjdk";
+            default = true;
+          }
+        ];
       };
+
+      # Seed a *writable* settings.json (not a store symlink) so extensions like
+      # kilo-code can edit it at runtime. `force = false` in the config means HM
+      # only writes it when absent, preserving kilo's later edits across `switch`.
+      settingsJson = pkgs.writeText "vscode-user-settings" (
+        builtins.toJSON coreSettings
+      );
     in
     {
       options.chiasson.home.editors.vscode = {
@@ -48,14 +82,19 @@
       };
 
       config = lib.mkIf (root.enable && cfg.enable) {
-        home.packages = [ pkgs.vscode ];
+        home.packages = [ ];
+
+        # Writable, seed-once user settings (kilo-code can append to it).
+        home.file.".config/Code/User/settings.json" = {
+          source = settingsJson;
+          force = false;
+        };
 
         programs.vscode = {
           enable = true;
-          package = pkgs.vscode;
+          package = vscodeWithJdk;
           extensions = defaultExtensions ++ cfg.extensions;
-          userSettings = coreSettings;
         };
       };
     };
-}
+  }