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/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,