v0.3: 6-layer architecture complete

Layers:
  Layer 1: XDP/eBPF — TCP state machine, SYN throttle, blacklist, ringbuf
  Layer 2: PoW Challenge — SHA-256 hashcash, dynamic difficulty, constant-time verify
  Layer 3: Rust Core — HMAC handshake, rate limit, death code (existing)
  Layer 4: Velocity — Physics check, CAPTCHA, protocol verification
  Layer 5: Paper — Heartbeat, auto-registration (existing)
  Layer 6: Traffic Intel — EWMA, 168h profiling, reputation, alerts

Infra: XDP→Prometheus metrics, ClickHouse + Grafana dashboard, Docker Compose
Testing: 100-IP DDoS simulation, MHDDoS ref analysis, load test report
Fixes: VarInt sign extension UB, pure ACK deadlock, RST/FIN cleanup
Ref: MHDDoS, Sonar, LimboFilter, AtomGuard, Infrarust, MC-XDP-eBPF, PowGo

crates/rampart-core/src/xdp/stats.rs

@@ -0,0 +1,11 @@
+#[derive(Debug, Clone, Copy, Default)]
+pub struct XdpStats {
+    pub total: u64,
+    pub tcp_mc: u64,
+    pub whitelist: u64,
+    pub blacklist: u64,
+    pub syn_throttle: u64,
+    pub passed: u64,
+    pub dropped: u64,
+    pub verified: u64,
+}