feat: TypeScript telemetry client SDK v0.1.0

Standalone npm package (@mosaicstack/telemetry-client) for reporting
task-completion telemetry and querying predictions from the Mosaic
Stack Telemetry server.

- TelemetryClient with setInterval-based background flush
- EventQueue (bounded FIFO array)
- BatchSubmitter with native fetch, exponential backoff, Retry-After
- PredictionCache (Map + TTL)
- EventBuilder with auto-generated event_id/timestamp
- Zero runtime dependencies (Node 18+ native APIs)
- 43 tests, 86% branch coverage

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/prediction-cache.ts

@@ -0,0 +1,59 @@
+import { PredictionQuery, PredictionResponse } from './types/predictions.js';
+
+interface CacheEntry {
+  response: PredictionResponse;
+  expiresAt: number;
+}
+
+/**
+ * In-memory cache for prediction responses with TTL-based expiry.
+ */
+export class PredictionCache {
+  private readonly cache = new Map<string, CacheEntry>();
+  private readonly ttlMs: number;
+
+  constructor(ttlMs: number) {
+    this.ttlMs = ttlMs;
+  }
+
+  /** Build a deterministic cache key from a prediction query. */
+  private buildKey(query: PredictionQuery): string {
+    return `${query.task_type}:${query.model}:${query.provider}:${query.complexity}`;
+  }
+
+  /** Get a cached prediction. Returns null if not cached or expired. */
+  get(query: PredictionQuery): PredictionResponse | null {
+    const key = this.buildKey(query);
+    const entry = this.cache.get(key);
+
+    if (!entry) {
+      return null;
+    }
+
+    if (Date.now() > entry.expiresAt) {
+      this.cache.delete(key);
+      return null;
+    }
+
+    return entry.response;
+  }
+
+  /** Store a prediction response with TTL. */
+  set(query: PredictionQuery, response: PredictionResponse): void {
+    const key = this.buildKey(query);
+    this.cache.set(key, {
+      response,
+      expiresAt: Date.now() + this.ttlMs,
+    });
+  }
+
+  /** Clear all cached predictions. */
+  clear(): void {
+    this.cache.clear();
+  }
+
+  /** Number of entries currently in cache (including potentially expired). */
+  get size(): number {
+    return this.cache.size;
+  }
+}