Fix Java upgrade notification flow telemetry and activation check

Follow-up improvements from v0.27.5 telemetry analysis
(devdiv-azure-service-dmitryr/azure-java-migration-copilot-vscode-extension#5979):

1. Add a source field (SOURCE_CVE / SOURCE_JAVA_UPGRADE) to the
   upgradeNotification.show event so NOTIFY-level data can be split by
   CVE vs upgrade and aligned with downstream funnel stages.
2. Replace the fixed setTimeout(2000) post-install activation wait with a
   15s polling loop to fix the false activation-timeout rate.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: FrankLiu4138

src/upgrade/display/notificationManager.ts

@@ -93,6 +93,7 @@ class NotificationManager implements IUpgradeIssuesRenderer {
                 sendInfo(operationId, {
                     operationName: "java.dependency.upgradeNotification.show",
                     extensionState,
+                    source: hasCVEIssue ? Upgrade.SOURCE_CVE : Upgrade.SOURCE_JAVA_UPGRADE,
                 });
 
                 const buttons = hasCVEIssue

src/upgrade/utility.ts

@@ -221,11 +221,15 @@ export async function checkOrInstallAppModExtensionForUpgrade(
 
         await checkOrPromptToEnableAppModExtension("upgrade");
 
-        // Wait briefly for the newly installed extension to activate
-        await new Promise(resolve => setTimeout(resolve, 2000));
+        // installExtension resolves on install completion, not when the extension's
+        // activate() has run, so poll for the target state instead of a fixed sleep.
+        const deadline = Date.now() + 15000;
+        let newState = getExtensionState(extensionIdToCheck);
+        while (newState !== "up-to-date" && Date.now() < deadline) {
+            await new Promise(resolve => setTimeout(resolve, 500));
+            newState = getExtensionState(extensionIdToCheck);
+        }
 
-        // Re-check if the newly installed extension is active and meets version requirement
-        const newState = getExtensionState(extensionIdToCheck);
         const canProceed = newState === "up-to-date";
         sendInfo(operationId, {
             operationName: "java.dependency.upgradeFlow.result",