Function close_pane_as 

pub(crate) async fn close_pane_as(
    state: &AppState,
    caller_agent_id: &str,
    own_block_id: &str,
    target_block_id: &str,
    reason: Option<&str>,
    via: &str,
) -> (StatusCode, Value)

Close the pane that holds target_block_id on behalf of caller_agent_id (whose own pane is own_block_id), the way ClosePane does: a pane the caller is in closes at once; another agent’s pane waits 15 s for its user to keep it (§6.5) and answers 202 with the pending request. Audited as pane.close. Shared by ClosePane and RunCommand’s pane:close (server/ui_shortcuts.rs), so both carry the same protection. via names the tool in the pending request and the audit.