fix(core): Resolve TypeScript strict mode and ES client API compatibility issues for v3.0.0

- Fix ES client v8+ API: use document/doc instead of body for index/update operations
- Add type assertions (as any) for ES client ILM, template, and search APIs
- Fix strict null checks with proper undefined handling (nullish coalescing)
- Fix MetricsCollector interface to match required method signatures
- Fix Logger.error signature compatibility in plugins
- Resolve TermsQuery type index signature conflict
- Remove sourceMap from tsconfig (handled by tsbuild with inlineSourceMap)

ts/examples/kv/kv-store-example.ts

@@ -9,7 +9,6 @@ import {
   ElasticsearchConnectionManager,
   LogLevel,
   KVStore,
-  type KVStoreConfig,
 } from '../../index.js';
 
 interface UserSession {