Bootstrap DD3 Rust port workspace with host-first compatibility tests

fuzz/fuzz_targets/chunk_stream_ingest.rs

@@ -0,0 +1,35 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+
+fuzz_target!(|data: &[u8]| {
+    let mut state = dd3_protocol::ReassemblyState::default();
+    let mut buffer = [0u8; 4096];
+
+    let mut pos = 0usize;
+    while pos + 7 <= data.len() {
+        let batch_id = u16::from_le_bytes([data[pos], data[pos + 1]]);
+        let idx = data[pos + 2];
+        let cnt = data[pos + 3];
+        let total_len = u16::from_le_bytes([data[pos + 4], data[pos + 5]]);
+        let chunk_len = data[pos + 6] as usize;
+        pos += 7;
+        if pos + chunk_len > data.len() {
+            break;
+        }
+        let chunk = &data[pos..pos + chunk_len];
+        pos += chunk_len;
+
+        let _ = dd3_protocol::push_chunk(
+            &mut state,
+            batch_id,
+            idx,
+            cnt,
+            total_len,
+            chunk,
+            0,
+            5000,
+            4096,
+            &mut buffer,
+        );
+    }
+});