pub(crate) fn prune_old_captures(dir: &Path)Expand description
Same bug class, same fix, as agentmux-srv’s prune_old_screenshots
(ui_handlers.rs, reagent P2, PR #2662) — reapplied here per reagent’s
review of this tool’s own PR (#2709 round 1), which found it wasn’t
reused. Best-effort, on the write path, PNG-only.