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/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")>();