Add benchmark results for fast3 and fast4, implement KeepAliveLspBridge, and add tests for staged strategies

- Added new benchmark result files: compare_2026-02-09_score_fast3.json and compare_2026-02-09_score_fast4.json.
- Implemented KeepAliveLspBridge to maintain a persistent LSP connection across multiple queries, improving performance.
- Created unit tests for staged clustering strategies in test_staged_stage3_fast_strategies.py, ensuring correct behavior of score and dir_rr strategies.

ccw/src/core/services/rate-limiter.ts

@@ -0,0 +1,49 @@
+export interface RateLimitResult {
+  ok: boolean;
+  remaining: number;
+  resetAt: number;
+}
+
+interface BucketState {
+  tokens: number;
+  resetAt: number;
+}
+
+/**
+ * Simple fixed-window token bucket (in-memory).
+ * Good enough for local dashboard usage; not suitable for multi-process deployments.
+ */
+export class RateLimiter {
+  private buckets = new Map<string, BucketState>();
+  private limit: number;
+  private windowMs: number;
+
+  constructor(opts: { limit: number; windowMs: number }) {
+    this.limit = Math.max(0, opts.limit);
+    this.windowMs = Math.max(1, opts.windowMs);
+  }
+
+  consume(key: string, cost: number = 1): RateLimitResult {
+    const now = Date.now();
+    const safeCost = Math.max(0, Math.floor(cost));
+    const existing = this.buckets.get(key);
+
+    if (!existing || now >= existing.resetAt) {
+      const resetAt = now + this.windowMs;
+      const nextTokens = this.limit - safeCost;
+      const ok = nextTokens >= 0;
+      const tokens = ok ? nextTokens : this.limit;
+      this.buckets.set(key, { tokens, resetAt });
+      return { ok, remaining: Math.max(0, ok ? tokens : 0), resetAt };
+    }
+
+    const nextTokens = existing.tokens - safeCost;
+    if (nextTokens < 0) {
+      return { ok: false, remaining: Math.max(0, existing.tokens), resetAt: existing.resetAt };
+    }
+
+    existing.tokens = nextTokens;
+    return { ok: true, remaining: nextTokens, resetAt: existing.resetAt };
+  }
+}
+