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/build.rs

@@ -0,0 +1,42 @@
+use std::path::PathBuf;
+use std::process::Command;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let has_xdp_feature = std::env::var("CARGO_FEATURE_XDP").is_ok();
+    if !has_xdp_feature {
+        return Ok(());
+    }
+
+    let manifest_dir = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR")?);
+    let xdp_dir = manifest_dir.join("../../xdp");
+    let out_dir = PathBuf::from(std::env::var("OUT_DIR")?);
+
+    let src = xdp_dir.join("xdp_filter.c");
+    let dst = out_dir.join("xdp_filter.o");
+
+    println!("cargo:rerun-if-changed={}", src.display());
+
+    let host_arch = std::env::var("HOST").unwrap_or_default();
+    let status = Command::new("clang")
+        .args([
+            "-O2",
+            "-g",
+            "-target",
+            "bpf",
+            "-mcpu=v3",
+            "-c",
+            src.to_str().ok_or("src path is not valid UTF-8")?,
+            "-o",
+            dst.to_str().ok_or("dst path is not valid UTF-8")?,
+            &format!("-I{}", xdp_dir.display()),
+            &format!("-I/usr/include/{}-linux-gnu", host_arch),
+        ])
+        .status()?;
+
+    if !status.success() {
+        return Err("XDP C compilation failed (see clang errors above)".into());
+    }
+
+    println!("cargo:rerun-if-env-changed=CARGO_FEATURE_XDP");
+    Ok(())
+}