fix(timeline): retain child state and recover rewinds on resume

Provider children now live in the parent's timeline next to its history,
so their descriptors, rows and retirements survive close, archive and a
manager rebuilt over the same backend, and deleting the agent removes
them all. Resuming settles a rewind that was still open when the runtime
stopped instead of leaving its rows half-retired.

A stored child's status is only the last report, possibly from provider
history or an earlier runtime. Workspace activity and idle cleanup now
read the children the current runtime reported running, and closing a
runtime cancels only those, so a child stored as running from an earlier
runtime no longer keeps the agent busy or blocks cleanup.

docs/data-model.md

@@ -175,6 +175,14 @@ Terminal activity contributes to the workspace status bucket **per `workspaceId`
 
 ---
 
+## Runtime-only Agent Timelines
+
+Agent timelines are not written to `$PASEO_HOME`. `AgentTimeline` owns each agent's history behind
+a backend, and the only backend is in memory, so a daemon restart loses it and the next resume
+imports provider history. See [owned history](timeline-sync.md#owned-history).
+
+---
+
 ## 2. Daemon Configuration
 
 **Path:** `$PASEO_HOME/config.json`