fix(swift): fall back to Ubuntu 24.04 for unsupported Ubuntu versions

Swift only provides binaries for Ubuntu 20.04, 22.04, and 24.04.
On newer Ubuntu versions (e.g. 26.04), the download URL would 404.
Now maps unsupported Ubuntu versions to 24.04.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jdx

src/plugins/core/swift.rs

@@ -279,7 +279,11 @@ fn platform_directory() -> String {
         let settings = Settings::get();
         let arch = settings.arch();
         if os_release.id == "ubuntu" && arch == "arm64" {
-            let retval = format!("{}{}-aarch64", os_release.id, os_release.version_id);
+            let retval = format!(
+                "{}{}-aarch64",
+                os_release.id,
+                ubuntu_swift_version(&os_release.version_id)
+            );
             retval.replace(".", "")
         } else {
             platform().replace(".", "")
@@ -304,6 +308,8 @@ fn platform() -> String {
             "ubi9".to_string() // only 9 is available
         } else if os_release.id == "fedora" {
             "fedora39".to_string() // only 39 is available
+        } else if os_release.id == "ubuntu" {
+            format!("ubuntu{}", ubuntu_swift_version(&os_release.version_id))
         } else {
             format!("{}{}", os_release.id, os_release.version_id)
         }
@@ -336,6 +342,15 @@ fn architecture(settings: &Settings) -> Option<&str> {
     None
 }
 
+/// Swift only provides Ubuntu binaries for specific versions.
+/// Map unsupported Ubuntu versions to the latest supported one.
+fn ubuntu_swift_version(version_id: &str) -> &str {
+    match version_id {
+        "20.04" | "22.04" | "24.04" => version_id,
+        _ => "24.04",
+    }
+}
+
 fn url(tv: &ToolVersion) -> String {
     let settings = Settings::get();
     format!(