Add invite strings (waste: URI) for peer onboarding

- internal/invite: Encode/Decode waste:<base64json{anchor,network}>
- proto: CmdGenerateInvite + EvtInviteGenerated + InviteString field
- ipc: track active network name; handle generate_invite (returns invite
  string when joined to a network, errors if not joined or no anchor)
- daemon: --join <invite> flag — decodes anchor URL + network name,
  sets anchor and auto-joins on startup
- tui: --join <invite> flag — extracts network name, skips -network
  requirement; ctrl+i generates invite and shows it full-screen;
  Esc dismisses the invite overlay
- FUTURE.md: document multi-network derived-identity design

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/ipc/ipc.go

@@ -16,6 +16,7 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"github.com/waste-go/internal/invite"
 	"github.com/waste-go/internal/mesh"
 	"github.com/waste-go/internal/proto"
 )
@@ -24,8 +25,9 @@ import (
 type JoinFunc func(ctx context.Context, networkName string)
 
 // Run starts the IPC listener. Blocks until the listener fails.
+// anchorURL is the configured anchor WebSocket URL (used for invite generation).
 // Network join/leave state is daemon-scoped (shared across all IPC clients).
-func Run(m *mesh.Mesh, port int, join JoinFunc) error {
+func Run(m *mesh.Mesh, port int, anchorURL string, join JoinFunc) error {
 	addr := fmt.Sprintf("127.0.0.1:%d", port)
 	ln, err := net.Listen("tcp", addr)
 	if err != nil {
@@ -33,11 +35,12 @@ func Run(m *mesh.Mesh, port int, join JoinFunc) error {
 	}
 	log.Printf("ipc: listening on %s", addr)
 
-	// networkCancel is shared across all clients — any client can join/leave,
-	// and the join persists even after the commanding client disconnects.
+	// networkCancel / networkName are shared across all clients — any client
+	// can join/leave, and the join persists after the commanding client disconnects.
 	var (
 		networkMu     sync.Mutex
 		networkCancel context.CancelFunc
+		networkName   string
 	)
 
 	doJoin := func(name string) {
@@ -47,6 +50,7 @@ func Run(m *mesh.Mesh, port int, join JoinFunc) error {
 		}
 		ctx, cancel := context.WithCancel(context.Background())
 		networkCancel = cancel
+		networkName = name
 		networkMu.Unlock()
 		go join(ctx, name)
 	}
@@ -56,21 +60,28 @@ func Run(m *mesh.Mesh, port int, join JoinFunc) error {
 		if networkCancel != nil {
 			networkCancel()
 			networkCancel = nil
+			networkName = ""
 		}
 		networkMu.Unlock()
 	}
 
+	currentNetwork := func() string {
+		networkMu.Lock()
+		defer networkMu.Unlock()
+		return networkName
+	}
+
 	for {
 		conn, err := ln.Accept()
 		if err != nil {
 			return fmt.Errorf("ipc accept: %w", err)
 		}
 		log.Printf("ipc: UI client connected from %s", conn.RemoteAddr())
-		go handleClient(conn, m, doJoin, doLeave)
+		go handleClient(conn, m, anchorURL, currentNetwork, doJoin, doLeave)
 	}
 }
 
-func handleClient(conn net.Conn, m *mesh.Mesh, doJoin func(string), doLeave func()) {
+func handleClient(conn net.Conn, m *mesh.Mesh, anchorURL string, currentNetwork func() string, doJoin func(string), doLeave func()) {
 	defer conn.Close()
 
 	events := m.Subscribe()
@@ -187,6 +198,23 @@ func handleClient(conn net.Conn, m *mesh.Mesh, doJoin func(string), doLeave func
 				Rooms:          []string{"general"},
 			})
 
+		case proto.CmdGenerateInvite:
+			net := currentNetwork()
+			if net == "" {
+				send(errMsg("generate_invite: not currently joined to a network"))
+				continue
+			}
+			if anchorURL == "" {
+				send(errMsg("generate_invite: daemon was started without -anchor flag"))
+				continue
+			}
+			inv, err := invite.Encode(anchorURL, net)
+			if err != nil {
+				send(errMsg(fmt.Sprintf("generate_invite: %v", err)))
+				continue
+			}
+			send(proto.IpcMessage{Type: proto.EvtInviteGenerated, InviteString: inv})
+
 		case proto.CmdSendFile:
 			send(errMsg("file transfer not yet implemented"))