loops: reorder history collapsed under the progress pill

Completes the reorder rationale loop — the previous commit captured
REORDER: markers server-side but nothing surfaced them. Now the loops
sidebar renders a small "N reorders ▸" button under the progress pill
whenever the loop has any reorder events. Click expands to a
newest-first list of "iter <n> · <rationale>" lines so a reviewer can
see, at a glance, when the plan was adjusted and why.

Backend:
- LoopProgress DTO gains recent_reorders: Vec<Value> — newest-first,
  capped at 5 so the card stays compact. Full history remains on the
  loop row's reorder_events column.
- cm_db::repo::loops::recent_reorders — reads the jsonb array, returns
  the last N in newest-first order.
- list_progress populates it per loop.

Frontend:
- LoopReorderEvent + recent_reorders on LoopProgress type.
- LoopsList tracks openHistoryId per-loop (one open at a time).
- Card renders history button + expanded panel styled to match the
  progress pill above.

Notes:
- The event object schema is {run_id, iteration, text, ts}. Fields are
  optional in the TS type so future schema tweaks don't break the
  render.
- 5-item cap chosen so the sidebar card doesn't grow unbounded. If a
  loop accumulates a lot of reorders, follow-up UI can render the full
  history on the loop detail page.

frontend/src/components/dashboard/LoopsList.tsx

@@ -46,6 +46,7 @@ export function LoopsList({
   const noAgents = agents.length === 0;
   const [loops, setLoops] = useState<Loop[]>([]);
   const [progress, setProgress] = useState<Map<string, LoopProgress>>(new Map());
+  const [openHistoryId, setOpenHistoryId] = useState<string | null>(null);
   const [loading, setLoading] = useState(true);
   const [wizardOpen, setWizardOpen] = useState(false);
   const [editing, setEditing] = useState<Loop | null>(null);
@@ -334,6 +335,69 @@ export function LoopsList({
                     );
                   })()}
                 </button>
+                {(() => {
+                  const p = progress.get(l.id);
+                  if (!p || p.recent_reorders.length === 0) return null;
+                  const open = openHistoryId === l.id;
+                  return (
+                    <div style={{ marginTop: 2 }}>
+                      <button
+                        type="button"
+                        onClick={() =>
+                          setOpenHistoryId(open ? null : l.id)
+                        }
+                        style={{
+                          all: "unset",
+                          cursor: "pointer",
+                          fontFamily: mono,
+                          fontSize: 9.5,
+                          color: "#8a8a92",
+                          display: "flex",
+                          alignItems: "center",
+                          gap: 6,
+                        }}
+                        aria-expanded={open}
+                      >
+                        <span style={{ opacity: 0.7 }}>{open ? "▾" : "▸"}</span>
+                        <span>
+                          {p.recent_reorders.length} reorder
+                          {p.recent_reorders.length === 1 ? "" : "s"}
+                        </span>
+                      </button>
+                      {open ? (
+                        <div
+                          style={{
+                            marginTop: 4,
+                            padding: "6px 8px",
+                            borderRadius: 6,
+                            background: "rgba(255,255,255,.02)",
+                            border: "1px solid rgba(255,255,255,.05)",
+                            display: "flex",
+                            flexDirection: "column",
+                            gap: 5,
+                          }}
+                        >
+                          {p.recent_reorders.map((e, i) => (
+                            <div
+                              key={`${e.run_id ?? "unk"}-${i}`}
+                              style={{
+                                fontFamily: mono,
+                                fontSize: 10,
+                                color: "#c3c3c8",
+                                lineHeight: 1.4,
+                              }}
+                            >
+                              <span style={{ color: "#8a8a92" }}>
+                                iter {e.iteration ?? "?"} ·{" "}
+                              </span>
+                              {e.text ?? ""}
+                            </div>
+                          ))}
+                        </div>
+                      ) : null}
+                    </div>
+                  );
+                })()}
 
                 {confirming ? (
                   <div