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-c0re/assets/app.js

@@ -167,6 +167,10 @@
           ' ',
           form('/destroy/' + c.name, 'btn-destroy', 'DESTR0Y',
             'destroy ' + c.name + '? container is removed; state + creds kept.'),
+          ' ',
+          form('/destroy/' + c.name, 'btn-destroy', 'PURG3',
+            'PURGE ' + c.name + '? container, config history, claude creds, '
+            + 'and /state/ notes are all WIPED. no undo.', { purge: 'on' }),
         );
       }
       ul.append(li);