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.

CLAUDE.md

@@ -337,7 +337,9 @@ loops over every stale container.
 Container row buttons (rendered per-state by `assets/app.js`):
 
 - Always: `↻ R3BU1LD` (calls `lifecycle::rebuild`), and for sub-agents
-  `DESTR0Y` (container removed, state + creds kept).
+  `DESTR0Y` (container removed, state + creds kept) + `PURG3`
+  (DESTR0Y plus wipes `/var/lib/hyperhive/{agents,applied}/<name>/`;
+  no undo).
 - Running: `↺ R3ST4RT` + (sub-agents only) `■ ST0P`.
 - Stopped: `▶ ST4RT`.
 - Stale marker: clickable `needs update ↻` badge (same target as rebuild