Add fleet registry removal with confirm modal and agent_removed WS.

Operators can remove machines from Crucible and dashboard rosters with honest messaging that deletion is registry-only; bulk select, oath ledger entries, and Go/Vitest coverage included.

server/web/src/help/uiHelp.test.ts

@@ -106,6 +106,8 @@ describe('UI_HELP', () => {
     'crucible_btn_cf_tunnel',
     'fl_filter_chips',
     'fl_bulk_actions',
+    'fl_delete_roster',
+    'crucible_delete_roster',
     'fl_groups',
     'set_alerts',
     'set_alert_notifications',

server/web/src/help/uiHelp.ts

@@ -218,7 +218,11 @@ export const UI_HELP: Record<string, string> = {
   fl_filter_chips:
     'Narrow the roster by name/IP/notes/tags (text search), tag label, subnet prefix, minimum 15m hashrate, or the "needs attention" flag (offline or idle miners below 100 H/s).',
   fl_bulk_actions:
-    'Actions applied to every checked agent at once: pause or resume mining, stop the miner thread, restart only idle workers, take a screenshot (one agent only), or permanently delete from roster.',
+    'Actions applied to every checked agent at once: pause or resume mining, stop the miner thread, restart only idle workers, take a screenshot (one agent only), or remove from fleet registry (does not uninstall on host).',
+  fl_delete_roster:
+    'Remove from fleet deletes the server registry row and disconnects a live session. It does not uninstall the agent binary on the machine — use Remote Actions → Uninstall for that.',
+  crucible_delete_roster:
+    'Per-machine fleet registry removal from Crucible notes panel or the active-target bar. Offline agents can be removed; online agents are kicked from the hub first.',
   fl_groups:
     'Named color-coded subsets of the fleet stored in browser local storage. Click a chip to check-select all members — then apply bulk actions or send Crucible commands to the whole group at once.',