refactor(hive-ag3nt): split hive bin into hive-agent / hive-agent-mcp / hive-agent-wake

docs/agent-hierarchy.md

@@ -214,7 +214,8 @@ nspawn agent. Open questions, not yet wired:
 
 ## Harness systemd unit shape
 
-One harness binary (`hive`), one `harness-base.nix` template, one
+One harness serve binary (`hive-agent`, with its `hive-agent-mcp` /
+`hive-agent-wake` siblings), one `harness-base.nix` template, one
 service unit (`systemd.services.hive-ag3nt`) for all agents. There
 is no longer a separate manager service name or role distinction in
 the harness — privilege differences live server-side in the broker
@@ -259,7 +260,8 @@ bit set` regardless of `hyperhive.user.passwordlessSudo`.
 
 ### `serviceConfig` highlights
 
-- `ExecStart = pkgs.hyperhive/bin/hive serve` — single binary.
+- `ExecStart = pkgs.hyperhive/bin/hive-agent` — same binary for
+  every agent.
 - `Restart = on-failure`, `RestartSec = 2` — keeps the harness
   resilient across transient crashes without thundering retries.
 - `RuntimeDirectory = "hive-config"` → `/run/hive-config/` owned by