fix(workspace): unify nested project discovery and run ownership (#1716)

* fix(build): scope Kotlin bridge to linked Maven modules

* fix(run): resolve nested Go modules for context runs

* fix(gradle): discover nested builds and select compatible JVMs

* fix(workspace): share project discovery and module ownership

* fix(run): keep root toolchains for nested modules and resolve them once per module

- Python run configurations of a nested module without its own virtualenv use the closest one up to the project root.
- Gradle builds and runs fall back to the JDK matching the project's Java version when the Gradle version is unknown.
- Module-local interpreters and toolchains are resolved lazily, once per owning module.
- Tests build expected paths per segment so they hold on Windows.

crates/ide-sdk/src/java.rs

@@ -540,10 +540,12 @@ pub fn project_java_version(module_dir: &Path) -> Option<u32> {
     }
     for name in ["build.gradle.kts", "build.gradle"] {
         let Some(text) = read(name) else { continue };
-        if let Some(i) = text.find("JavaLanguageVersion.of(") {
-            let rest = &text[i + "JavaLanguageVersion.of(".len()..];
-            if let Some(v) = parse_java_version(rest.split(')').next().unwrap_or_default()) {
-                return Some(v);
+        for key in ["JavaLanguageVersion.of(", "jvmToolchain("] {
+            if let Some(i) = text.find(key) {
+                let rest = &text[i + key.len()..];
+                if let Some(v) = parse_java_version(rest.split(')').next().unwrap_or_default()) {
+                    return Some(v);
+                }
             }
         }
         for key in ["sourceCompatibility", "targetCompatibility"] {
@@ -1138,6 +1140,14 @@ mod tests {
         assert_eq!(project_java_version(dir), Some(11));
         std::fs::write(dir.join("build.gradle.kts"), "sourceCompatibility = '1.8'").unwrap();
         assert_eq!(project_java_version(dir), Some(8));
+        for (script, version) in [
+            ("kotlin { jvmToolchain(21) }", Some(21)),
+            ("kotlin { jvmToolchain(17) }", Some(17)),
+            ("kotlin { jvmToolchain(projectVersion) }", None),
+        ] {
+            std::fs::write(dir.join("build.gradle.kts"), script).unwrap();
+            assert_eq!(project_java_version(dir), version);
+        }
     }
 }