fix(daily): keep the coach check-in constants out of the client bundle

The Today hero and the check-in hook imported the check-in intent constants
from digest.ts, which — since the milestone slice — transitively reaches the
database through the streak baseline engine. That pulled the Postgres driver
into the client bundle (a Turbopack 'Can't resolve net/tls/dns' build failure
the worktree build couldn't surface). Move the four constants to a tiny,
dependency-free coach-checkin-intents module; the client imports them from
there, and digest.ts (the server builder) stays server-only.

src/app/api/coach/plans/[id]/route.ts

@@ -34,7 +34,7 @@ import { prisma } from "@/lib/db";
 import { requireModuleEnabled } from "@/lib/modules/gate";
 import { checkRateLimit, rateLimitHeaders } from "@/lib/rate-limit";
 import { decryptFromBytes } from "@/lib/ai/coach/bytes-codec";
-import { COACH_CHECKIN_REVIEW_DAYS } from "@/lib/daily/digest";
+import { COACH_CHECKIN_REVIEW_DAYS } from "@/lib/daily/coach-checkin-intents";
 import { coachPlanPatchSchema } from "@/lib/validations/coach-plan";
 
 interface RouteCtx {