DaemonManager: rpcTask not saved — stopWatching() can't cancel it

[AprilNEA]

Problem

connectAndWatch() creates rpcTask as a local variable (line 286). stopWatching() cancels watchTask but has no reference to rpcTask. After cancellation, rpcTask may still write to a dead continuation.

File: Packages/ArcBoxClient/Sources/ArcBoxClient/DaemonManager.swift:286-299

Fix

Save rpcTask as an instance variable. Cancel it in stopWatching() alongside watchTask.

[linear]

ABXD-82