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-agent-mcp/src/mcp/args.rs

@@ -94,7 +94,7 @@ pub struct CompactArgs {
 }
 
 // -----------------------------------------------------------------------------
-// Privileged tool arg types (lifecycle, approvals, scheduling)
+// Privileged tool arg types (lifecycle, approvals)
 // -----------------------------------------------------------------------------
 
 #[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
@@ -123,89 +123,3 @@ pub struct CancelLooseEndArgs {
     /// Row id from the matching `get_loose_ends` entry.
     pub id: i64,
 }
-
-#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
-pub struct RequestSchedulePromptArgs {
-    /// Recipient agents — one schedule fires to many inboxes at the
-    /// scheduled time. `operator` is not a valid target — she isn't a
-    /// container with a todo inbox to push a wake into, and this is
-    /// for fanning a prompt out to agents, not scheduling something
-    /// at her.
-    pub targets: Vec<String>,
-    /// Message body delivered to each target's inbox at fire time.
-    /// Same size budget as `send` bodies.
-    pub body: String,
-    /// Absolute unix timestamp (seconds) for the FIRST fire. For
-    /// recurring schedules the worker re-arms in
-    /// `interval_seconds` steps from this point on.
-    pub first_fire_at_unix: i64,
-    /// `None` / absent = one-shot. `Some(n > 0)` = recurring every
-    /// `n` seconds. The worker clamps catch-up so a long downtime
-    /// fires ONCE on resume (skipped-cycle count surfaces in the
-    /// per-target `last_result`), not N delayed pulses in a row.
-    #[serde(default)]
-    pub interval_seconds: Option<u64>,
-    /// Optional description shown on the dashboard approval card +
-    /// preserved on the schedule row for later operator reference.
-    #[serde(default)]
-    pub description: Option<String>,
-}
-
-#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
-pub struct FireScheduleNowArgs {
-    /// Schedule id to fire out of band. Get this from a prior
-    /// `list_schedules` call or the approval-resolved event for
-    /// the originating `request_schedule_prompt`.
-    pub id: i64,
-}
-
-#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
-pub struct CancelScheduleArgs {
-    /// Schedule id from a prior `list_schedules` call or the
-    /// approval-resolved event for a `request_schedule_prompt`.
-    pub id: i64,
-    /// Optional target list. `None` / empty = cancel the entire
-    /// schedule. `Some(["alice", "bob"])` = cancel just those
-    /// recipients (the schedule keeps firing for any remaining
-    /// active targets, and auto-cancels its parent row when every
-    /// target is gone).
-    #[serde(default)]
-    pub targets: Option<Vec<String>>,
-}
-
-#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
-pub struct EditScheduleArgs {
-    /// Schedule id from a prior `list_schedules` call or the
-    /// approval-resolved event for a `request_schedule_prompt`.
-    pub id: i64,
-    /// New body text. Omit to keep the existing one.
-    #[serde(default)]
-    pub body: Option<String>,
-    /// New description. Omit to keep the existing one. (To CLEAR
-    /// the description, use the dashboard PATCH endpoint
-    /// directly — the agent surface intentionally keeps the args
-    /// flat / non-nullable to dodge the doubly-wrapped Option
-    /// schemars quirk; clearing fields is rare and operator-side.)
-    #[serde(default)]
-    pub description: Option<String>,
-    /// Recurring interval in seconds. Omit to keep the existing
-    /// cadence; pass an explicit value to set a new one. Toggling
-    /// recurring↔one-shot (clearing the interval) is operator-only
-    /// for the same reason as `description` above.
-    #[serde(default)]
-    pub interval_seconds: Option<u64>,
-    /// New absolute unix timestamp for the next fire. Omit to
-    /// leave the schedule on its current cadence.
-    #[serde(default)]
-    pub next_fire_at_unix: Option<i64>,
-    /// Names of new targets to add. Replace-on-conflict: re-adding
-    /// a previously cancelled target resets its history (operator
-    /// intent on re-add = "this target is active again").
-    #[serde(default)]
-    pub targets_add: Option<Vec<String>>,
-    /// Names of targets to cancel. Tombstones preserve per-target
-    /// audit; when no active targets remain the schedule
-    /// auto-cancels.
-    #[serde(default)]
-    pub targets_remove: Option<Vec<String>>,
-}