feat(coach): close the plan check-in loop on the Today rail

Every accepted coach plan now earns a gentle weekly check-in. Confirming a
plan (proposed → active) without an explicit review date defaults one to a
week out, so a plan is always reviewed, not only the coach's own experiments.

The daily digest emits a single `coach_checkin` rail item when a standing
plan's review has come due — its pinned review date, or a defaulted
activation + 7 days for plans that predate it, or the read-back state a
reviewed plan carries. Capped at one check-in a day across all plans
(earliest-due wins); the rest wait for a following day. It reads existing
plan state only — no fresh generation, nothing warms on mount, and it is
gated on the coach module.

The card offers three one-tap actions through the existing plan-lifecycle
route: keep it (re-arm for another week), adjust it (open the coach), or let
it go (a guilt-free, respected end — the calm inversion of a streak). An
ignored check-in sits quiet and stops resurfacing after about two cycles;
its status is never changed behind the user's back.

Copy lands in all six locales.

e2e/dashboard.spec.ts

@@ -130,6 +130,31 @@ test.describe("authenticated dashboard render", () => {
                   },
                 ],
               },
+              // S3 — a coach check-in card (keep / adjust / let-go). Rendered
+              // only; the mutating taps PATCH the plan route, which this spec
+              // never clicks, so it stays green without a plan-route stub.
+              {
+                kind: "coach_checkin",
+                title: "Time to check in on a plan",
+                body: "About a week ago you set: “every morning → weigh in”.",
+                status: "info",
+                moduleKey: "coach",
+                actions: [
+                  {
+                    labelKey: "daily.action.checkinKeep",
+                    intent: "coach.checkin.keep:p1",
+                  },
+                  {
+                    labelKey: "daily.action.checkinAdjust",
+                    intent: "coach.checkin.adjust",
+                    href: "/coach",
+                  },
+                  {
+                    labelKey: "daily.action.checkinLetGo",
+                    intent: "coach.checkin.letGo:p1",
+                  },
+                ],
+              },
             ],
           },
           error: null,