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/core/observability/logger.ts

@@ -199,9 +199,26 @@ export class Logger {
 
   /**
    * Log at ERROR level
+   *
+   * Accepts either:
+   * - error(message, Error, meta) - explicit error with optional metadata
+   * - error(message, meta) - error context as metadata (error property extracted)
    */
-  error(message: string, error?: Error, meta?: Record<string, unknown>): void {
-    this.log(LogLevel.ERROR, message, meta, error);
+  error(message: string, errorOrMeta?: Error | Record<string, unknown>, meta?: Record<string, unknown>): void {
+    if (errorOrMeta instanceof Error) {
+      this.log(LogLevel.ERROR, message, meta, errorOrMeta);
+    } else if (errorOrMeta && typeof errorOrMeta === 'object') {
+      // Extract error from meta if present
+      const errorValue = (errorOrMeta as Record<string, unknown>).error;
+      const extractedError = errorValue instanceof Error
+        ? errorValue
+        : typeof errorValue === 'string'
+          ? new Error(errorValue)
+          : undefined;
+      this.log(LogLevel.ERROR, message, errorOrMeta, extractedError);
+    } else {
+      this.log(LogLevel.ERROR, message);
+    }
   }
 
   /**