docs: scheduled prompts are swarm-level; the hive page is a read-only list

Drops docs/tools/scheduling.md and every description of hive-level
schedule creation, the worker, the removed MCP tools, the scheduling tool
group and the removed endpoints/events, pointing at docs/swarm/schedules.md.

Cargo.lock

@@ -1769,7 +1769,6 @@ dependencies = [
  "clap_complete",
  "forgejo-api",
  "futures-util",
- "hive-agent-sock",
  "hive-core-agent-sock",
  "hive-host-sock",
  "hive-jobq",
@@ -1777,7 +1776,6 @@ dependencies = [
  "hive-log",
  "hive-priv-sock",
  "hive-sh4re",
- "hive-sock-client",
  "hive-types",
  "hmac 0.13.0",
  "indicatif",