P2-02 (server side): schedule reconciliation push + ack handling

Server is now the source of truth for the agent's cron set.

* Helpers in schedule_push.go:
  - loadScheduleSetPayload reads the host's schedules + canonical
    version into the wire shape.
  - pushScheduleSetOnConn writes directly to a just-handshaken conn
    (avoids racing against Hub.Register on a brand-new connection).
  - pushScheduleSetAsync is the post-CRUD flavour — no-op when the
    host is offline (the next reconnect's on-hello path catches it
    up, so a missed push is non-fatal).
  - applyScheduleAck records what version the agent has confirmed.

* onAgentHello restructured: was returning early when the host had
  no repo credentials, which made the schedule push unreachable for
  fresh hosts. Split into pushRepoCredsOnHello (silent no-op on
  ErrNotFound) + pushScheduleSetOnConn (always runs). Empty schedule
  list is a valid push: tells the agent to drop stale cron entries.

* WS dispatcher gains an OnScheduleAck hook on HandlerDeps; the
  http server wires it to applyScheduleAck. MsgScheduleAck moves
  out of the "TODO(P2)" group into a real case that decodes the
  payload and forwards to the callback.

* Schedule CRUD handlers each fire pushScheduleSetAsync after the
  audit-log write so the agent picks up changes within seconds.

Tests cover:
  - On-hello push of an already-created schedule, agent acks,
    applied_schedule_version flips on the host row.
  - Connect-then-CRUD: empty initial push (version 0), then a
    follow-on push at version 1 after the operator creates a
    schedule via REST.

Agent-side `schedule.set` handler (parse, replace local cron,
emit `schedule.ack`) is the remainder of P2-02 and lands with
P2-03's local scheduler.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tasks.md

@@ -98,7 +98,7 @@ Sizes: **S** = under a day, **M** = 1–3 days, **L** = 3–7 days.
 ## Phase 2 — Scheduling, retention, repo operations
 
 - [x] **P2-01** (M) Schedule schema + CRUD API. `schedules` table was already laid down in 0001; this slice adds `store.Schedule`/`RetentionPolicy`/`ScheduleOptions` types, `CreateSchedule` / `GetSchedule` / `ListSchedulesByHost` / `UpdateSchedule` / `DeleteSchedule` / `GetHostScheduleVersion` / `SetHostAppliedScheduleVersion` (mutations bump `host_schedule_version` atomically in-tx), and REST endpoints `GET|POST /api/hosts/{id}/schedules` + `PUT|DELETE /api/hosts/{id}/schedules/{sid}`. Validation: cron-expr parses via `robfig/cron/v3` (same parser the agent will use, so anything that validates here will fire there); kind ∈ {backup, forget, prune, check} (init/unlock are operator-only); backup schedules require ≥1 path; hooks rejected on non-backup kinds (spec §14.3). Mutations audit-logged. Server + store tests cover the happy path, validation, and version bumps.
-- [ ] **P2-02** (L) Server-pushed schedule reconciliation (server is source of truth; agent applies)
+- [~] **P2-02** (L) Server-pushed schedule reconciliation. Server side complete: `pushScheduleSet*` helpers (one for the on-hello window, one for the post-CRUD async flavour), wiring in `onAgentHello` (always pushes, even when the host has no repo creds yet), `pushScheduleSetAsync` called from Create/Update/Delete handlers (no-op when the host is offline; on-hello catches up). `MsgScheduleAck` is now handled in the WS dispatcher: `OnScheduleAck` callback persists `applied_schedule_version`. Server-side end-to-end test covers (a) on-hello push of an already-created schedule + ack round-trip + applied_version write-through, and (b) connect-then-CRUD push. **Remaining:** agent-side `schedule.set` handler that applies the new state to its local cron + emits `schedule.ack` — lands in P2-03.
 - [ ] **P2-03** (M) Agent local scheduler (`robfig/cron/v3`); persists next-fire times across restarts
 - [ ] **P2-04** (M) Schedule editor UI (paths, excludes, tags, cron, retention)
 - [ ] **P2-05** (M) `forget` command with retention policy (keep-last/daily/weekly/monthly/yearly)