Status line shows stale subagent description after subagent completes

Description

When a subagent (launched via the Agent tool) completes a long-running task, the parent conversation's status line continues displaying the subagent's task description indefinitely. This makes it appear that work is still in progress when it has already finished, leading to user confusion ("why is this taking so long?").

Steps to Reproduce

1. In a conversation, launch a subagent for a task that takes 1+ minutes (e.g., filing a cross-repo GitHub issue via gh issue create)
2. Wait for the subagent to complete
3. Observe the parent conversation's status line

Expected Behavior

The status line should update when the subagent completes — either clearing, reverting to the parent's current activity, or showing a completion indicator.

Actual Behavior

The status line continues showing the subagent's task description (e.g., "Filing gyro columns DCR in gnar-data-lake… (5m 3s)") with an incrementing timer, even though the subagent finished minutes ago. The stale description persists until the parent emits new output (e.g., the next tool call or text response).

Impact

• User sees a timer climbing and assumes work is blocked or hung
• Prompts unnecessary "why is this taking so long?" interruptions
• Erodes trust in the status line as a progress indicator

Environment

• Claude Code CLI on Windows 11
• Model: claude-opus-4-6
• Observed during multi-agent session with foreground subagents

🤖 Generated with Claude Code