refactor(background-agent): normalize task ID field naming

Rename BackgroundTask and attempt ID fields to camelCase across background-agent consumers while moving BackgroundManager construction to a single config object.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

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

src/tools/background-task/create-background-cancel.ts

@@ -41,7 +41,7 @@ export function createBackgroundCancel(manager: BackgroundManager, _client: Back
               id: task.id,
               description: task.description,
               status: originalStatus === "pending" ? "pending" : "running",
-              sessionID: task.sessionID,
+              sessionID: task.sessionId,
             })
           }
 
@@ -105,7 +105,7 @@ Status: ${task.status}`
 
 Task ID: ${task.id}
 Description: ${task.description}
-Session ID: ${task.sessionID}
+Session ID: ${task.sessionId}
 Status: ${task.status}`
       } catch (error) {
         return `[ERROR] Error cancelling task: ${error instanceof Error ? error.message : String(error)}`