Add per-staff metrics: StaffAction event log + /stats command

Event-sourced tracking of staff/ticket lifecycle actions, plus a /stats
command. Foundation for a future tickets-website analytics dashboard.

Data:
- StaffAction model (event log) + Ticket.game / Ticket.closedAt
- STATS_ADMIN_IDS config (who may view others' stats)

Recording (fire-and-forget, idempotent on real state transitions):
- claim, response (channel reply + /response send), escalate, de-escalate,
  transfer, close (4 sites), reopen — each denormalizes ticketType, tier,
  priority, game, requester (senderEmail / creatorId), guildId
- close events carry closerType / resolverId (claimer credit) / wasClaimed;
  transfer carries fromId / toId; reopen stamps resolverId
- conditional close transition helper (atomic open->closed + closedAt) shared
  by all four close paths

Query + command:
- pure period parser (presets + free-text) and stats shaper (per-metric keys)
- command-aware autocomplete dispatch
- /stats: period (autocomplete) + member (admin-gated) + source (all/email/
  discord), ManageMessages + staff-role gated, ephemeral, tier-labeled embed

288+ unit tests; timing/busiest-times data is collected but displayed later.

tests/autocompleteDispatch.test.js

@@ -0,0 +1,66 @@
+/**
+ * Phase 9 — command-aware autocomplete dispatcher tests.
+ *
+ * Uses the injectable _handlers parameter to test the dispatch seam without
+ * requiring real Tag/Ticket DB access.
+ *
+ * Covers:
+ *   (a) commandName 'response' → response handler called
+ *   (b) unknown commandName    → no handler called (no-op)
+ *   (c) handler receives the interaction object unchanged
+ */
+import { describe, it, expect, vi } from 'vitest';
+
+import { handleAutocomplete } from '../handlers/commands/index.js';
+
+function makeInteraction(commandName) {
+  return {
+    commandName,
+    options: {
+      getSubcommand: vi.fn().mockReturnValue('send'),
+      getFocused: vi.fn().mockReturnValue('')
+    },
+    respond: vi.fn().mockResolvedValue(undefined)
+  };
+}
+
+describe('autocomplete dispatcher', () => {
+  it('routes commandName "response" to the response handler', async () => {
+    const responseHandler = vi.fn().mockResolvedValue(undefined);
+    const interaction = makeInteraction('response');
+
+    await handleAutocomplete(interaction, { response: responseHandler });
+
+    expect(responseHandler).toHaveBeenCalledTimes(1);
+    expect(responseHandler).toHaveBeenCalledWith(interaction);
+  });
+
+  it('routes commandName "stats" to the stats handler', async () => {
+    const statsHandler = vi.fn().mockResolvedValue(undefined);
+    const interaction  = makeInteraction('stats');
+
+    await handleAutocomplete(interaction, { stats: statsHandler });
+
+    expect(statsHandler).toHaveBeenCalledTimes(1);
+    expect(statsHandler).toHaveBeenCalledWith(interaction);
+  });
+
+  it('no-ops for an unknown commandName', async () => {
+    const responseHandler = vi.fn().mockResolvedValue(undefined);
+    const interaction = makeInteraction('unknown-command');
+
+    await handleAutocomplete(interaction, { response: responseHandler });
+
+    expect(responseHandler).not.toHaveBeenCalled();
+  });
+
+  it('passes the interaction object through to the handler unchanged', async () => {
+    let received = null;
+    const handler = vi.fn().mockImplementation(async i => { received = i; });
+    const interaction = makeInteraction('response');
+
+    await handleAutocomplete(interaction, { response: handler });
+
+    expect(received).toBe(interaction);
+  });
+});