feat(#1106): split bash mcp into hive-bash-daemon + hive-bash-mcp bridge

- new hive-bash-mcp crate: daemon (subprocess runner, wake signals) +
  stdio bridge (mcp tools). mirrors hive-matrix-mcp architecture
- hive-ag3nt: remove bash_runner.rs and bash_run/bash_status mcp tools;
  get_loose_ends uses hive_bash_mcp:🏃:active_tasks() via crate dep
- harness-base.nix: add hive-bash-daemon systemd service + auto-inject
  bash extraMcpServer into every agent (socket: /run/hive-bash/socket)

hive-ag3nt/Cargo.toml

@@ -12,6 +12,7 @@ axum.workspace = true
 reqwest.workspace = true
 futures-util = "0.3"
 clap.workspace = true
+hive-bash-mcp = { path = "../hive-bash-mcp" }
 hive-sh4re.workspace = true
 rmcp.workspace = true
 rusqlite.workspace = true