refactor(background-agent): rename registerExternalTask to trackTask

Update BackgroundManager to rename the method for tracking external tasks, improving clarity and consistency in task management. Adjust related tests to reflect the new method name.

src/features/background-agent/manager.test.ts

@@ -960,7 +960,7 @@ describe("BackgroundManager.tryCompleteTask", () => {
   })
 })
 
-describe("BackgroundManager.registerExternalTask", () => {
+describe("BackgroundManager.trackTask", () => {
   let manager: BackgroundManager
 
   beforeEach(() => {
@@ -985,8 +985,8 @@ describe("BackgroundManager.registerExternalTask", () => {
     }
 
     // #when
-    await manager.registerExternalTask(input)
-    await manager.registerExternalTask(input)
+    await manager.trackTask(input)
+    await manager.trackTask(input)
 
     // #then
     const concurrencyManager = getConcurrencyManager(manager)
@@ -1010,7 +1010,7 @@ describe("BackgroundManager.resume concurrency key", () => {
 
   test("should re-acquire using external task concurrency key", async () => {
     // #given
-    const task = await manager.registerExternalTask({
+    const task = await manager.trackTask({
       taskId: "task-1",
       sessionID: "session-1",
       parentSessionID: "parent-session",