security: gate /help, signature modal submit, and cancel_delete_tag on staff role

Closes the remaining non-broccolini interaction paths after the prior
TICKET_BUTTON_HANDLERS gate. After this commit, every bot interaction is
staff-only except the panel buttons (open_ticket / open_ticket_thread /
open_ticket_channel) and their ticket-creation modal submit — those have
to stay public because they're how members and customers open tickets.

Specific changes:

- handlers/commands/index.js: handleCommand no longer has the
  `!== 'help'` carve-out. /help now goes through requireStaffRole like
  every other slash command. Non-staff get the same ephemeral
  "only available to the support team" reply.

- broccolini-discord.js: the signature_modal_* modal-submit handler now
  calls requireStaffRole before writing to StaffSignature. /signature
  already gates the modal display via the slash-command staff check;
  this is defense in depth against directly crafted submissions.

- handlers/buttons.js: cancel_delete_tag moved out of
  FREE_BUTTON_HANDLERS and gated alongside confirm_delete_tag::*. The
  dialog is only shown ephemerally to the staff who triggered
  /response delete, so non-staff can't reach it in normal flow; gating
  keeps the button surface consistent.

Kept public (by design — these are the customer entry points):
  open_ticket / open_ticket_thread / open_ticket_channel buttons
  ticket_modal / ticket_modal_thread / ticket_modal_channel submits

handlers/buttons.js

@@ -707,12 +707,15 @@ async function postTicketWelcomeEmbeds(channel, interaction, email, game, descri
 // Dispatch tables
 // ============================================================
 
-/** Buttons that don't depend on a ticket-bound channel. */
+/**
+ * Public-facing buttons that don't require a staff role: the panel buttons
+ * that any member uses to open a ticket. Customer-facing entry points stay
+ * here. cancel_delete_tag is staff-only and gated separately in handleButton.
+ */
 const FREE_BUTTON_HANDLERS = {
   open_ticket: handleOpenTicketModal,
   open_ticket_thread: handleOpenTicketModal,
-  open_ticket_channel: handleOpenTicketModal,
-  cancel_delete_tag: handleTagDeleteCancel
+  open_ticket_channel: handleOpenTicketModal
 };
 
 /** Buttons that fire inside a ticket channel. The dispatcher does the lookup. */
@@ -739,8 +742,15 @@ async function handleButton(interaction) {
     return handleTagDeleteConfirm(interaction);
   }
 
-  // FREE_BUTTON_HANDLERS are public-facing: open_ticket* (panel buttons,
-  // anyone can open a ticket) and cancel_delete_tag (no-op cancel).
+  // Tag-delete cancel: paired with the staff-only delete flow; gate to keep
+  // the button surface consistent (non-staff can't reach the dialog anyway).
+  if (customId === 'cancel_delete_tag') {
+    if (await requireStaffRole(interaction)) return;
+    return handleTagDeleteCancel(interaction);
+  }
+
+  // FREE_BUTTON_HANDLERS are the public-facing panel buttons (open_ticket*).
+  // Customers/members must be able to click these to open a ticket.
   const freeHandler = FREE_BUTTON_HANDLERS[customId];
   if (freeHandler) return freeHandler(interaction);
 

handlers/commands/index.js

@@ -274,11 +274,11 @@ const CONTEXT_MENU_HANDLERS = {
 };
 
 /**
- * Slash-command dispatcher. /help is open to everyone; everything else
- * requires the staff role.
+ * Slash-command dispatcher. Every command is staff-only — including /help,
+ * which previously bypassed the role check.
  */
 async function handleCommand(interaction) {
-  if (interaction.commandName !== 'help' && (await requireStaffRole(interaction))) return;
+  if (await requireStaffRole(interaction)) return;
   const handler = COMMAND_HANDLERS[interaction.commandName];
   if (handler) await handler(interaction);
 }