chore(qa): Final Wave cleanup — resolve lint findings from F2 review

Production code (all findings cleared):
- GenerationHistory: drop unused fetchProHistory(userId) param,
  change let activeId to const
- InitiativeTracker: remove write-only currentSessionName state
- NotesPanel: remove unused isLoading flag
- Open5eReference: drop unused getCachedTranslation/setCachedTranslation
  imports; use fetchTranslation result directly instead of re-lookup
- ai/openrouter.ts: drop unused z + Monster imports; attach cause to
  rethrown AbortError
- ai/kimi.ts: drop unused z import
- api/dm/ai/generate.ts: annotate best-effort counter increment catch
- api/dm/ai/history.ts: drop unused sql import

Test files (trivial fixes; ~70 mock-related `as any` errors remain as
pre-existing tech debt across api test mocks):
- translation-client: drop unused MockBroadcastChannel _name param and
  unused getCachedTranslation destructure
- open5e-types: eslint-disable for the intentional type-test aliases
- {notes,initiative}-api: remove unused mockUser2 placeholder
- {notes,initiative,translate,history}-api: let mockDb -> const mockDb
- ai-generate-api: wrap deliberate `var` mock decls in eslint-disable
  with comment explaining vi.mock hoisting requirement

Verification: tsc 0 errors, vitest 339/339, lint 81 -> 70 errors
(production code fully clean; remaining errors are test-mock as-any
patterns from Waves 5-6).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/ai-generate-api.test.ts

@@ -37,11 +37,15 @@ function mockRequest(
   } as unknown as Request;
 }
 
+// vi.mock factories are hoisted, so refs they read must use var (not let/const)
+// to be visible at hoist time without ReferenceError.
+/* eslint-disable no-var */
 var mockOpenRouterNPC = vi.fn();
 var mockKimiNPC = vi.fn();
 var mockSearchMonsters = vi.fn();
 var mockCheckRateLimit = vi.fn();
 var mockIncrementCounter = vi.fn();
+/* eslint-enable no-var */
 
 vi.mock("@/lib/ai/openrouter", () => ({
   generateNPC: (...args: unknown[]) => mockOpenRouterNPC(...args),

tests/history-api.test.ts

@@ -96,7 +96,7 @@ function createMockDb() {
   };
 }
 
-let mockDb = createMockDb();
+const mockDb = createMockDb();
 
 vi.mock("drizzle-orm", async (importOriginal) => {
   const actual = await importOriginal<typeof import("drizzle-orm")>();

tests/initiative-api.test.ts

@@ -12,18 +12,6 @@ const mockUser = {
   createdAt: new Date("2024-01-01"),
 };
 
-const mockUser2 = {
-  id: 2,
-  vkId: null,
-  yandexId: null,
-  email: null,
-  name: "Other User",
-  avatar: null,
-  tier: "free" as const,
-  boostyVerifiedAt: null,
-  createdAt: new Date("2024-01-01"),
-};
-
 function mockRequest(
   url: string,
   origin: string,
@@ -132,7 +120,7 @@ function createMockDb() {
   };
 }
 
-let mockDb = createMockDb();
+const mockDb = createMockDb();
 
 vi.mock("drizzle-orm", async (importOriginal) => {
   const actual = await importOriginal<typeof import("drizzle-orm")>();

tests/notes-api.test.ts

@@ -12,18 +12,6 @@ const mockUser = {
   createdAt: new Date("2024-01-01"),
 };
 
-const mockUser2 = {
-  id: 2,
-  vkId: null,
-  yandexId: null,
-  email: null,
-  name: "Other User",
-  avatar: null,
-  tier: "free" as const,
-  boostyVerifiedAt: null,
-  createdAt: new Date("2024-01-01"),
-};
-
 function mockRequest(
   url: string,
   origin: string,
@@ -132,7 +120,7 @@ function createMockDb() {
   };
 }
 
-let mockDb = createMockDb();
+const mockDb = createMockDb();
 
 vi.mock("drizzle-orm", async (importOriginal) => {
   const actual = await importOriginal<typeof import("drizzle-orm")>();

tests/open5e-types.test.ts

@@ -5,6 +5,7 @@ import type { Monster, Spell } from "../src/lib/open5e/client";
 // If a listed key is missing from the interface, TypeScript will error at compile time.
 type AssertKeys<T, K extends keyof T> = K;
 
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
 type _MonsterHasAllFields = AssertKeys<
   Monster,
   | "name"
@@ -34,6 +35,7 @@ type _MonsterHasAllFields = AssertKeys<
   | "condition_immunities"
 >;
 
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
 type _SpellHasAllFields = AssertKeys<
   Spell,
   | "name"

tests/translate-api.test.ts

@@ -77,7 +77,7 @@ function createMockDb() {
   };
 }
 
-let mockDb = createMockDb();
+const mockDb = createMockDb();
 
 vi.mock("drizzle-orm", async (importOriginal) => {
   const actual = await importOriginal<typeof import("drizzle-orm")>();

tests/translation-client.test.ts

@@ -3,7 +3,7 @@ import { describe, it, expect, vi, beforeEach } from "vitest";
 const mockPostMessage = vi.fn();
 const mockAddEventListener = vi.fn();
 
-function MockBroadcastChannel(this: unknown, _name: string) {
+function MockBroadcastChannel(this: unknown) {
   return {
     postMessage: mockPostMessage,
     addEventListener: mockAddEventListener,
@@ -75,7 +75,6 @@ describe("translation service", () => {
     global.fetch = mockFetch as unknown as typeof fetch;
 
     const {
-      getCachedTranslation,
       setCachedTranslation,
       fetchTranslation,
       clearTranslationCache,