feat: add HTTP and JSON benchmarks

New benchmarks:
- http_benchmark.lux: Minimal HTTP server for throughput testing
  - Use with wrk or ab for request/second measurements
  - Target: > 50k req/sec

- json_benchmark.lux: JSON parsing performance test
  - Token counting simulation
  - Measures iterations per second

These complement the existing recursive benchmarks (fib, ackermann)
with web-focused performance tests.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

benchmarks/http_benchmark.lux

@@ -0,0 +1,37 @@
+// HTTP Server Benchmark
+//
+// A minimal HTTP server for benchmarking request throughput.
+// Run with: lux benchmarks/http_benchmark.lux
+//
+// Test with:
+//   wrk -t4 -c100 -d10s http://localhost:8080/
+//   OR
+//   ab -n 10000 -c 100 http://localhost:8080/
+//
+// Expected: > 50k req/sec on modern hardware
+
+fn handleRequest(request: { method: String, path: String, body: String }): { status: Int, body: String } with {Console} = {
+    // Minimal JSON response for benchmarking
+    { status: 200, body: "{\"status\":\"ok\"}" }
+}
+
+fn serveLoop(): Unit with {Console, HttpServer} = {
+    let request = HttpServer.accept()
+    let response = handleRequest(request)
+    HttpServer.respond(response.status, response.body)
+    serveLoop()
+}
+
+fn main(): Unit with {Console, HttpServer} = {
+    Console.print("HTTP Benchmark Server")
+    Console.print("Listening on port 8080...")
+    Console.print("")
+    Console.print("Test with:")
+    Console.print("  wrk -t4 -c100 -d10s http://localhost:8080/")
+    Console.print("  ab -n 10000 -c 100 http://localhost:8080/")
+    Console.print("")
+    HttpServer.listen(8080)
+    serveLoop()
+}
+
+let result = run main() with {}