feat(maven): choose the JRE Maven runs with (#2020)

Closes #1976. Settings › Build Tools › Maven gets a JRE field (per project or global): empty uses the Project JDK, else the chosen JDK runs Maven sync, builds, goals and tests (JAVA_HOME). One resolver (ide_sdk::apply::maven_jdk / maven_build_env) now serves the build model, compile steps, Maven run configurations and the mvnd Java 17 check; an explicit JAVA_HOME in a run configuration still wins.

src/features/settings/__tests__/languages.test.ts

@@ -27,7 +27,13 @@ describe("languages settings", () => {
         jdtlsVmArgs: " -Xmx2g ",
         jdk: 21,
         jdtlsJdk: " /opt/jdk-25 ",
-        maven: { home: " /opt/maven ", daemon: "yes", mvndHome: " /opt/mvnd ", threads: " 2C " },
+        maven: {
+          runnerJre: " /opt/jdk-21 ",
+          home: " /opt/maven ",
+          daemon: "yes",
+          mvndHome: " /opt/mvnd ",
+          threads: " 2C ",
+        },
       },
     });
     expect(v.python).toEqual({ interpreter: "/usr/bin/python3", activateVirtualenv: true });
@@ -39,6 +45,7 @@ describe("languages settings", () => {
     expect(v.java.jdk).toBe("");
     expect(v.java.jdtlsJdk).toBe("/opt/jdk-25");
     expect(v.java.maven).toEqual({
+      runnerJre: "/opt/jdk-21",
       home: "/opt/maven",
       userSettings: "",
       localRepository: "",
@@ -52,6 +59,13 @@ describe("languages settings", () => {
     expect(validateLanguages({ java: { maven: { threads: 4 } } }).java.maven.threads).toBe("");
   });
 
+  it("defaults the Maven runner JRE to the project JDK and preserves a chosen JDK", () => {
+    expect(validateSettings({}).languages.java.maven.runnerJre).toBe("");
+    expect(validateLanguages({ java: { maven: { runnerJre: 21 } } }).java.maven.runnerJre).toBe("");
+    const settings = validateSettings({ languages: { java: { maven: { runnerJre: " ./jdks/21 " } } } });
+    expect(validateSettings(settings).languages.java.maven.runnerJre).toBe("./jdks/21");
+  });
+
   it("keeps the Ruby interpreter through settings normalization and defaults to Auto", () => {
     expect(validateSettings({}).languages.ruby.interpreter).toBe("");
     expect(validateLanguages({ ruby: { interpreter: 42 } }).ruby.interpreter).toBe("");

src/features/settings/__tests__/mavenRunner.test.tsx

@@ -0,0 +1,45 @@
+import { cleanup, fireEvent, render, screen } from "@testing-library/react";
+import { afterEach, beforeEach, expect, it } from "vitest";
+import { PageContext } from "../components/context";
+import { MavenPage } from "../languages/LanguagePages";
+import { useSdks } from "../languages/api";
+import { DEFAULT_SETTINGS } from "../model/schema";
+import { stagedValue, useSettingsDialog } from "../model/staging";
+import { EXECUTION_PAGES } from "../pages/execution";
+
+beforeEach(() => {
+  useSettingsDialog.setState({
+    base: structuredClone(DEFAULT_SETTINGS),
+    globalBase: structuredClone(DEFAULT_SETTINGS),
+    staged: {},
+    query: "",
+  });
+  useSdks.setState({
+    byKind: {
+      jdk: [{ path: "/jdks/21", home: "/jdks/21", name: "JDK 21", version: "21", source: "system", extra: null }],
+      maven: [],
+    },
+    loading: {},
+  });
+});
+afterEach(cleanup);
+
+it("chooses an installed Maven runner JRE in project scope and returns to Project JDK", () => {
+  const page = EXECUTION_PAGES.find((p) => p.id === "build.maven")!;
+  expect(page.projectScope).toBe(true);
+  expect(page.defaultScope).toBe("project");
+  expect(page.keywords).toEqual(expect.arrayContaining(["JRE", "runner", "JDK", "JAVA_HOME"]));
+  render(
+    <PageContext.Provider value={{ pageId: page.id, scope: page.defaultScope! }}>
+      <MavenPage />
+    </PageContext.Provider>,
+  );
+  expect(screen.getByRole("button", { name: "JRE" })).toHaveTextContent("Use Project JDK");
+  fireEvent.click(screen.getByRole("button", { name: "JRE" }));
+  fireEvent.click(screen.getByRole("option", { name: /JDK 21/ }));
+  expect(stagedValue(useSettingsDialog.getState(), "project", "languages.java.maven.runnerJre")).toBe("/jdks/21");
+  expect(stagedValue(useSettingsDialog.getState(), "global", "languages.java.maven.runnerJre")).toBe("");
+  fireEvent.click(screen.getByRole("button", { name: "JRE" }));
+  fireEvent.click(screen.getByRole("option", { name: "Use Project JDK" }));
+  expect(stagedValue(useSettingsDialog.getState(), "project", "languages.java.maven.runnerJre")).toBe("");
+});

src/features/settings/languages/LanguagePages.tsx

@@ -498,6 +498,16 @@ export function MavenPage() {
   return (
     <div className={styles.page}>
       <Section>
+        <SdkRow
+          k="languages.java.maven.runnerJre"
+          label="JRE"
+          kind="jdk"
+          emptyLabel="Use Project JDK"
+          directory
+          browseTitle="Select JDK Home Directory"
+          aria-label="JRE"
+          hint="JDK used for Maven sync, builds, goals and tests. An explicit JAVA_HOME in a run configuration takes precedence."
+        />
         <SdkRow
           k="languages.java.maven.home"
           label="Maven home path"

src/features/settings/pages/execution.tsx

@@ -145,6 +145,10 @@ export const EXECUTION_PAGES: PageSpec[] = [
     // IntelliJ IDEA: Build Tools › Maven, before Console / Debugger.
     order: 359,
     keywords: [
+      "JRE",
+      "runner",
+      "JDK",
+      "JAVA_HOME",
       "maven home",
       "mvn",
       "mvnw",