hive-c0re stops owning scheduled prompts; agents lose the schedule tools

Scheduled prompts are swarm-level now (swarmctl schedule, #4936). The hive
keeps the rows it has only so the operator can copy them over.

- hive-c0re no longer fires anything: the scheduled-prompts worker is gone,
  and with it every create/edit/cancel/pause/resume/fire path (dashboard
  endpoints, agent-socket verbs, the SchedulePrompt approval kind and its
  approve handler). The store keeps open + list; GET /api/schedules stays.
- A v6 approvals migration drops schedule_prompt rows.
- Nothing submits approvals any more, so the submit path goes too:
  Approvals::submit_kind (now a test fixture), the ApprovalAdded dashboard
  event and its emitter.
- Coordinator::push_todo, whose only caller was the worker, goes, and with
  it hive_host_sock::agent_todo_socket and hive-c0re's hive-agent-sock /
  hive-sock-client deps.
- The schedules_changed dashboard event goes; nothing mutates the rows.
- Agents lose request_schedule_prompt, cancel_schedule, fire_schedule_now,
  edit_schedule and list_schedules, the `scheduling` tool group, their
  system-prompt line and their transcript formatters. `remind` is unchanged.

hive-host-sock/src/lib.rs

@@ -76,20 +76,6 @@ pub fn agent_web_socket(name: &Ident) -> PathBuf {
         .join("web.sock")
 }
 
-/// Per-agent in-container todo socket path —
-/// `AGENT_SOCKET_DIR/<name>/agent.sock`. Same socket the harness's
-/// `HIVE_AGENT_SOCKET` binds and in-container producers (matrix/bash/
-/// forge-notify) already dial — `hive-c0re` uses this to push a todo
-/// directly into a *running* agent's local store (see
-/// `Coordinator::push_todo`); the container being down (socket absent)
-/// means the push is simply skipped, not queued.
-#[must_use]
-pub fn agent_todo_socket(name: &Ident) -> PathBuf {
-    PathBuf::from(AGENT_SOCKET_DIR)
-        .join(name.as_str())
-        .join("agent.sock")
-}
-
 /// nspawn machine-name prefix for agent containers (`h-<name>`). A single
 /// `starts_with(AGENT_PREFIX)` filter enumerates managed containers.
 pub const AGENT_PREFIX: &str = "h-";