refactor(background-agent): optimize lifecycle and simplify tools (#1411)

* refactor(background-agent): optimize cache timer lifecycle and result handling

Ultraworked with Sisyphus

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* refactor(background-task): simplify tool implementation and expand test coverage

Ultraworked with Sisyphus

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

* fix(background-task): fix BackgroundCancel tool parameter handling

Correct parameter names and types in BackgroundCancel tool to match actual usage patterns. Add comprehensive test coverage for parameter validation.

---------

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/background-task/tools.ts

@@ -638,28 +638,18 @@ export function createBackgroundCancel(manager: BackgroundManager, client: Backg
           }> = []
 
           for (const task of cancellableTasks) {
-            if (task.status === "pending") {
-              manager.cancelPendingTask(task.id)
-              cancelledInfo.push({
-                id: task.id,
-                description: task.description,
-                status: "pending",
-                sessionID: undefined,
-              })
-            } else if (task.sessionID) {
-              client.session.abort({
-                path: { id: task.sessionID },
-              }).catch(() => {})
-
-              task.status = "cancelled"
-              task.completedAt = new Date()
-              cancelledInfo.push({
-                id: task.id,
-                description: task.description,
-                status: "running",
-                sessionID: task.sessionID,
-              })
-            }
+            const originalStatus = task.status
+            const cancelled = await manager.cancelTask(task.id, {
+              source: "background_cancel",
+              abortSession: originalStatus === "running",
+            })
+            if (!cancelled) continue
+            cancelledInfo.push({
+              id: task.id,
+              description: task.description,
+              status: originalStatus === "pending" ? "pending" : "running",
+              sessionID: task.sessionID,
+            })
           }
 
           const tableRows = cancelledInfo
@@ -679,7 +669,7 @@ Continuable sessions:
 ${resumableTasks.map(t => `- \`${t.sessionID}\` (${t.description})`).join("\n")}`
              : ""
 
-          return `Cancelled ${cancellableTasks.length} background task(s):
+          return `Cancelled ${cancelledInfo.length} background task(s):
 
 | Task ID | Description | Status | Session ID |
 |---------|-------------|--------|------------|
@@ -697,13 +687,15 @@ ${resumeSection}`
 Only running or pending tasks can be cancelled.`
         }
 
-        if (task.status === "pending") {
-          // Pending task: use manager method (no session to abort, no slot to release)
-          const cancelled = manager.cancelPendingTask(task.id)
-          if (!cancelled) {
-            return `[ERROR] Failed to cancel pending task: ${task.id}`
-          }
+        const cancelled = await manager.cancelTask(task.id, {
+          source: "background_cancel",
+          abortSession: task.status === "running",
+        })
+        if (!cancelled) {
+          return `[ERROR] Failed to cancel task: ${task.id}`
+        }
 
+        if (task.status === "pending") {
           return `Pending task cancelled successfully
 
 Task ID: ${task.id}
@@ -711,18 +703,6 @@ Description: ${task.description}
 Status: ${task.status}`
         }
 
-        // Running task: abort session
-        // Fire-and-forget: abort 요청을 보내고 await 하지 않음
-        // await 하면 메인 세션까지 abort 되는 문제 발생
-        if (task.sessionID) {
-          client.session.abort({
-            path: { id: task.sessionID },
-          }).catch(() => {})
-        }
-
-        task.status = "cancelled"
-        task.completedAt = new Date()
-
         return `Task cancelled successfully
 
 Task ID: ${task.id}