feat: add comprehensive benchmark suite with flake commands

- Add nix flake commands: bench, bench-poop, bench-quick
- Add hyperfine and poop to devShell
- Document benchmark results with hyperfine/poop output
- Explain why Lux matches C (gcc's recursion optimization)
- Add HTTP server benchmark files (C, Rust, Zig)
- Add Zig versions of all benchmarks

Key findings:
- Lux (compiled): 28.1ms - fastest
- C (gcc -O3): 29.0ms - 1.03x slower
- Rust: 41.2ms - 1.47x slower
- Zig: 47.0ms - 1.67x slower

The performance comes from gcc's aggressive recursion-to-loop
transformation, which LLVM (Rust/Zig) doesn't perform as aggressively.

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

benchmarks/http_server.c

@@ -0,0 +1,47 @@
+// Minimal HTTP server benchmark - C version (single-threaded, poll-based)
+// Compile: gcc -O3 -o http_c http_server.c
+// Test: wrk -t2 -c50 -d5s http://localhost:8080/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+
+#define PORT 8080
+#define RESPONSE "HTTP/1.1 200 OK\r\nContent-Type: application/json\r\nContent-Length: 15\r\n\r\n{\"status\":\"ok\"}"
+
+int main() {
+    int server_fd, client_fd;
+    struct sockaddr_in address;
+    int opt = 1;
+    char buffer[1024];
+    socklen_t addrlen = sizeof(address);
+
+    server_fd = socket(AF_INET, SOCK_STREAM, 0);
+    setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
+    setsockopt(server_fd, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof(opt));
+
+    address.sin_family = AF_INET;
+    address.sin_addr.s_addr = INADDR_ANY;
+    address.sin_port = htons(PORT);
+
+    bind(server_fd, (struct sockaddr*)&address, sizeof(address));
+    listen(server_fd, 1024);
+
+    printf("C HTTP server listening on port %d\n", PORT);
+    fflush(stdout);
+
+    while (1) {
+        client_fd = accept(server_fd, (struct sockaddr*)&address, &addrlen);
+        if (client_fd < 0) continue;
+
+        read(client_fd, buffer, sizeof(buffer));
+        write(client_fd, RESPONSE, strlen(RESPONSE));
+        close(client_fd);
+    }
+
+    return 0;
+}