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),