hive-bash-mcp: add kill tool to stop a running or pending bash task

hive-bash-mcp/src/protocol.rs

@@ -18,6 +18,10 @@ pub enum TaskStatus {
     TimedOut,
     /// Daemon was restarted while the task was running; process is gone.
     Interrupted,
+    /// Killed on request via `BashKill` (SIGINT or SIGKILL to the task's
+    /// process group). Distinct from `Interrupted` (daemon-restart) and
+    /// `TimedOut` (exceeded `timeout_secs`).
+    Killed,
 }
 
 /// Task metadata + result written to `<id>.json` under the tasks dir.
@@ -93,6 +97,17 @@ pub enum DaemonRequest {
     /// Used by the harness `get_loose_ends` to surface active
     /// background work.
     ActiveTasks,
+
+    /// Kill a running (or still-pending) task. `force = false` sends
+    /// `SIGINT` to the task's process group (graceful — the process can
+    /// clean up); `force = true` sends `SIGKILL` (immediate). Signalling
+    /// the whole process group reaps `sh -c` plus any children it spawned,
+    /// so a runaway grandchild (e.g. `cargo`/`nix`) is actually stopped.
+    BashKill {
+        id: String,
+        #[serde(default)]
+        force: bool,
+    },
 }
 
 /// Response shape from the daemon. `Ok` carries a JSON payload; `Error`