destroy --purge: also wipe agent state dirs

new --purge flag on the destroy verb (cli + admin socket + dashboard).
default destroy still keeps /var/lib/hyperhive/{agents,applied}/<name>/
so recreating with the same name reuses prior config + creds.
with --purge, both dirs go too (config history, claude creds, /state/
notes). no undo. dashboard adds a separate PURG3 button with an
explicit confirmation copy; the existing DESTR0Y button keeps the
soft semantics.

claude.md dashboard-action-surface section updated; todo entry
dropped.

hive-sh4re/src/lib.rs

@@ -27,8 +27,15 @@ pub enum HostRequest {
     /// Tear down a sub-agent container: stop + remove + drop the systemd
     /// drop-in, purge pending approvals. Persistent state (proposed/applied
     /// repos, Claude credentials) is KEPT by default — recreating the agent
-    /// with the same name reuses prior config + login. Manager not destroyable.
-    Destroy { name: String },
+    /// with the same name reuses prior config + login. With `purge=true`
+    /// the agent's `/var/lib/hyperhive/{agents,applied}/<name>/` trees are
+    /// also wiped (config history + creds + notes gone forever). Manager
+    /// not destroyable.
+    Destroy {
+        name: String,
+        #[serde(default)]
+        purge: bool,
+    },
     /// Apply pending config to a managed container.
     Rebuild { name: String },
     /// List managed containers.