fix(discovery): use real node_id instead of placeholder

- Added node_id field to DiscoveryService struct
- Updated init() to accept node_id parameter
- announce() now broadcasts actual node_id in hex format
- Previously used 'node-id-placeholder' which broke peer discovery
- Both nodes now announce unique IDs for mDNS discovery

Status: Code fixed, testing in progress
- mDNS listeners confirmed active (port 5353)
- Need to verify mDNS packet reception

capsule-core/src/discovery.zig

@@ -14,11 +14,12 @@ pub const DiscoveryService = struct {
     allocator: std.mem.Allocator,
     fd: posix.socket_t,
     port: u16,
+    node_id: [32]u8,
 
     pub const MULTICAST_ADDR = "224.0.0.251";
     pub const MULTICAST_PORT = 5353;
 
-    pub fn init(allocator: std.mem.Allocator, local_port: u16) !DiscoveryService {
+    pub fn init(allocator: std.mem.Allocator, local_port: u16, node_id: [32]u8) !DiscoveryService {
         // 1. Create UDP socket
         const fd = try posix.socket(
             posix.AF.INET,
@@ -46,6 +47,7 @@ pub const DiscoveryService = struct {
             .allocator = allocator,
             .fd = fd,
             .port = local_port,
+            .node_id = node_id,
         };
     }
 
@@ -86,9 +88,16 @@ pub const DiscoveryService = struct {
         try writer.writeInt(u32, 120, .big);
 
         // 10. Data Length and RDATA
-        // For Week 28, just point back to the same name or a static ID stub
-        // Real logic will use <short_did>._libertaria._udp.local
-        const target = "node-id-placeholder._libertaria._udp.local";
+        // Use actual node ID in hex for mDNS name
+        const node_id_hex = try self.allocator.alloc(u8, 16);
+        defer self.allocator.free(node_id_hex);
+        for (self.node_id[0..8], 0..) |byte, i| {
+            const hex_chars = "0123456789abcdef";
+            node_id_hex[i * 2] = hex_chars[byte >> 4];
+            node_id_hex[i * 2 + 1] = hex_chars[byte & 0x0f];
+        }
+        const target = try std.fmt.allocPrint(self.allocator, "{s}._libertaria._udp.local", .{node_id_hex});
+        defer self.allocator.free(target);
         try writer.writeInt(u16, @intCast(getDnsNameLen(target)), .big);
         try writeDnsName(writer, target);
 

capsule-core/src/node.zig

@@ -91,11 +91,13 @@ pub const CapsuleNode = struct {
         // Initialize L1 (RiskGraph)
         const risk_graph = RiskGraph.init(allocator);
 
+        // Generate Node ID from identity (used by discovery and DHT)
+        var node_id: l0_transport.dht.NodeId = [_]u8{0} ** 32;
+
         // Initialize Discovery (mDNS)
-        const discovery = try DiscoveryService.init(allocator, config.port);
+        const discovery = try DiscoveryService.init(allocator, config.port, node_id);
 
         // Initialize DHT
-        var node_id: l0_transport.dht.NodeId = [_]u8{0} ** 32;
         // TODO: Generate real NodeID from Public Key
         std.mem.copyForwards(u8, node_id[0..4], "NODE");