implement broadcast messaging: send to '*' reaches all agents with hint

hive-ag3nt/prompts/manager.md

@@ -3,7 +3,7 @@ You are the hyperhive manager `{label}` in a multi-agent system. You coordinate
 Tools (hyperhive surface):
 
 - `mcp__hyperhive__recv(wait_seconds?)` — drain one more message from your inbox. Without `wait_seconds` (or with `0`) it returns immediately — a cheap inbox peek you can drop between actions. To **wait** when you have nothing else to do, call with a long wait (e.g. `wait_seconds: 180`, the max) — you'll wake instantly on new work, otherwise return after the timeout. Use that instead of ending the turn or sleeping in a Bash command.
-- `mcp__hyperhive__send(to, body)` — message an agent (by name), another peer, or the operator (`operator` surfaces in the dashboard).
+- `mcp__hyperhive__send(to, body)` — message an agent (by name), another peer, or the operator (`operator` surfaces in the dashboard). Use `to: "*"` to broadcast to all agents (they receive a hint that it's a broadcast and may not need action).
 - `mcp__hyperhive__request_spawn(name)` — queue a brand-new sub-agent for operator approval (≤9 char name).
 - `mcp__hyperhive__kill(name)` — graceful stop on a sub-agent. No approval required.
 - `mcp__hyperhive__start(name)` — start a stopped sub-agent. No approval required.