escalation: drop dead 'reason' param — never populated, always logged as null

The /escalate slash command never had a reason option in its definition
(commands/register.js only takes a 'level' option), so handleEscalate
hardcoded reason=null. The escalate button path passed null explicitly.
The log line wrote it verbatim as "Reason: null" on every escalate.

Remove the dead surface:
- runEscalation signature drops the reason parameter.
- The customer-facing email body drops the conditional reason suffix
  (`reason ? `\n\nReason: ${reason}` : ''`) — always-false branch.
- The logging-channel post drops "\nReason: ${reason}".
- handleEscalate drops the `const reason = null;` line and the call-site arg.
- handleEscalateButton (handlers/buttons.js) drops the trailing `null` arg.

If we ever want to capture a reason, the slash command would need a
StringOption('reason') and an escalate-modal for the button path —
neither exists today.

handlers/buttons.js

@@ -370,7 +370,7 @@ async function handleEscalateButton(interaction, ticket) {
     });
   }
 
-  await runDeferred(interaction, 'escalate', () => runEscalation(interaction, ticket, tier, null));
+  await runDeferred(interaction, 'escalate', () => runEscalation(interaction, ticket, tier));
 }
 
 async function handleDeescalateButton(interaction, ticket) {

handlers/commands/escalation.js

@@ -23,7 +23,7 @@ const Ticket = mongoose.model('Ticket');
  * Run escalation to a target tier (1 = tier 2, 2 = tier 3). Caller must
  * validate ticket and currentTier < nextTier, and have already deferred.
  */
-async function runEscalation(interaction, ticket, nextTier, reason) {
+async function runEscalation(interaction, ticket, nextTier) {
   const isDiscordTicket = ticket.gmailThreadId.startsWith('discord-');
   const categoryId = nextTier === 1
     ? (isDiscordTicket ? CONFIG.DISCORD_ESCALATED2_CHANNEL_ID : CONFIG.EMAIL_ESCALATED2_CHANNEL_ID)
@@ -87,7 +87,7 @@ async function runEscalation(interaction, ticket, nextTier, reason) {
     try {
       const escalatorName = interaction.member?.displayName || interaction.user.username;
       const tierLabel = nextTier === 1 ? 'tier 2' : 'tier 3';
-      const emailBody = `${escalatorName} escalated this ticket to ${tierLabel}.${reason ? `\n\nReason: ${reason}` : ''}`;
+      const emailBody = `${escalatorName} escalated this ticket to ${tierLabel}.`;
       await sendTicketNotificationEmail(ticket, null, emailBody, interaction.user.id);
     } catch (emailErr) {
       console.error('Escalation email failed (non-fatal):', emailErr.message);
@@ -108,7 +108,7 @@ async function runEscalation(interaction, ticket, nextTier, reason) {
     const ticketType = isDiscordTicket ? 'Discord' : 'Email';
     const tierLabel = nextTier === 1 ? 'tier 2' : 'tier 3';
     await enqueueSend(logChan,
-      `${ticketType} ticket ${interaction.channel} escalated to ${tierLabel} by ${interaction.user.tag}.\nReason: ${reason}`
+      `${ticketType} ticket ${interaction.channel} escalated to ${tierLabel} by ${interaction.user.tag}.`
     );
   }
 }
@@ -164,7 +164,6 @@ async function runDeescalation(interaction, ticket) {
 }
 
 async function handleEscalate(interaction) {
-  const reason = null;
   const level = interaction.options.getString('level');
   const nextTier = level === '3' ? 2 : 1;
 
@@ -192,7 +191,7 @@ async function handleEscalate(interaction) {
   }
 
   await runDeferred(interaction, 'escalate', () =>
-    runEscalation(interaction, ticket, nextTier, reason)
+    runEscalation(interaction, ticket, nextTier)
   );
 }