Fixes the Feature 13 review findings on the Discover deck (Maestro task 4fc551f0-3c11-4c15-b638-f2c08a28eb29): - F13-01: a batch failure (start, poll or job) is shown with its Retry whatever the deck has, so a replenish that fails while cards remain is no longer silent until the deck runs out. - F13-02: GET /api/v1/suggestions/deck reports the batch pending or running (active_batch, read in the deck's snapshot), and a decision that calls for a replenish returns the job of the batch it started or joined. The page follows a newly reported active batch, so a reopened page or a second session shows skeleton cards while the batch runs instead of "All caught up". - F13-03: ← / → leave the deck alone while it is inert behind a modal (the Quest log sheet or its confirmation). - F13-04: a one- or two-card deck keeps all three depths: skeleton cards stand in for the missing ones while a batch finds more Side quests, blank stack-edge cards while none is coming. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>