feat: implement Tier 3 features — lane queue, credential redaction, token dashboard, xAI, Voyage AI

- Lane Queue: per-session FIFO queue in gateway replacing reject-when-busy (9 tests)
- Credential Redaction: redactConfig() expanded to cover 18+ secret fields (16 tests)
- Web UI Token Dashboard: system.tokenUsage endpoint + Usage page with summary cards
- xAI (Grok) Provider: OpenAI-compatible client with model pricing
- Voyage AI Embeddings: new embedding provider with configurable dimensions (5 tests)
- Update gap analysis: 90→95 match (70%→74%), Tier 3 section marked DONE
- Update state.json: test count 1001→1034, add tier3_completion entry

Total: 1034 tests passing across 85 files, typecheck clean

src/gateway/session-bridge.ts

@@ -117,6 +117,50 @@ export class SessionBridge {
     return this.clients.size;
   }
 
+  /** Get usage stats for a specific connection's agent. */
+  getUsage(connectionId: string): { inputTokens: number; outputTokens: number; calls: number } | undefined {
+    const agent = this.clients.get(connectionId)?.agent;
+    return agent?.getUsage();
+  }
+
+  /** Get usage stats for all active sessions. Returns an array of per-session usage entries. */
+  getAllUsage(): Array<{
+    sessionId: string;
+    primary: { inputTokens: number; outputTokens: number; calls: number };
+    delegation: Record<string, { inputTokens: number; outputTokens: number; calls: number }>;
+    total: { inputTokens: number; outputTokens: number; calls: number; estimatedCost: number };
+  }> {
+    const results: Array<{
+      sessionId: string;
+      primary: { inputTokens: number; outputTokens: number; calls: number };
+      delegation: Record<string, { inputTokens: number; outputTokens: number; calls: number }>;
+      total: { inputTokens: number; outputTokens: number; calls: number; estimatedCost: number };
+    }> = [];
+
+    // De-duplicate by sessionId (multiple connections may share a session)
+    const seen = new Set<string>();
+
+    for (const client of this.clients.values()) {
+      if (seen.has(client.sessionId)) continue;
+      seen.add(client.sessionId);
+
+      const usage = client.agent.getUsage();
+      results.push({
+        sessionId: client.sessionId,
+        primary: { inputTokens: usage.inputTokens, outputTokens: usage.outputTokens, calls: usage.calls },
+        delegation: {} as Record<string, { inputTokens: number; outputTokens: number; calls: number }>,
+        total: {
+          inputTokens: usage.inputTokens,
+          outputTokens: usage.outputTokens,
+          calls: usage.calls,
+          estimatedCost: 0, // NativeAgent doesn't track cost; only AgentOrchestrator does
+        },
+      });
+    }
+
+    return results;
+  }
+
   private getOrCreateAgent(sessionId: string): NativeAgent {
     let agent = this.agents.get(sessionId);
     if (!agent) {