Add yaw2 invite interoperability

Protocol:
- invite.go: include full 64-char `net` hash in waste: invite blob
  (matches yaw2's `net` field — any client parsing the base64 JSON can
  join without knowing the plaintext name). Expose NetHash() helper.
- netmgr: add JoinByHash() — join via full 64-char hex hash alone,
  storing the short ID as display name. Enables joining yaw2 networks
  from a URL that only carries the hash.
- anchor: expose RunByHash() so netmgr can pass a pre-computed hash
  directly without a name→hash roundtrip.
- ipc/proto: add network_hash field to join_network — routes to
  JoinByHash when present and network_name is absent.

Web UI:
- Parse ?net=<64hex> (yaw2 URL param) and ?a=<anchor> in addition to
  existing ?n= / ?invite= params. Hash-only joins send network_hash.
- Sidebar shows yaw: contact card (yaw:<masterID>?n=<alias>) using the
  master identity — compatible with yaw2 contact card format. Click to
  copy to clipboard.

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

internal/netmgr/manager.go

@@ -147,6 +147,88 @@ func (mgr *Manager) Join(name, shareDir string) (string, error) {
 	return netID, nil
 }
 
+// JoinByHash joins a network using its pre-computed full 64-char hex hash
+// (yaw2 `net` field) instead of the plaintext name. The network is stored
+// with an empty name; the network_id (first 8 bytes) is used for display.
+// This enables joining networks whose names are unknown — e.g. from a yaw2
+// invite URL that only contains the hash.
+func (mgr *Manager) JoinByHash(netHash64, shareDir string) (string, error) {
+	if len(netHash64) != 64 {
+		return "", fmt.Errorf("netHash must be 64 hex chars, got %d", len(netHash64))
+	}
+	netID := netHash64[:16] // first 8 bytes = 16 hex chars
+
+	mgr.mu.Lock()
+	if _, exists := mgr.networks[netID]; exists {
+		mgr.mu.Unlock()
+		return netID, nil
+	}
+	mgr.mu.Unlock()
+
+	derived, err := crypto.DeriveForNetwork(mgr.cfg.MasterIdentity, netHash64)
+	if err != nil {
+		return "", fmt.Errorf("derive identity for net %s: %w", netID, err)
+	}
+
+	dbPath := filepath.Join(mgr.cfg.StoreDir, "messages-"+netID+".db")
+	st, err := store.Open(dbPath)
+	if err != nil {
+		return "", fmt.Errorf("open store for net %s: %w", netID, err)
+	}
+
+	m := mesh.New(derived, st)
+	if shareDir != "" {
+		m.ShareDir = shareDir
+	} else if mgr.cfg.ShareDir != "" {
+		m.ShareDir = mgr.cfg.ShareDir
+	}
+	m.DownloadDir = filepath.Join(mgr.cfg.StoreDir, "downloads-"+netID)
+
+	meshEvents := m.Subscribe()
+	go func() {
+		for evt := range meshEvents {
+			evt.NetworkID = netID
+			mgr.emit(evt)
+		}
+	}()
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	net := &Network{
+		ID:       netID,
+		Name:     netID, // display as short hash when name is unknown
+		Hash:     netHash64,
+		Identity: derived,
+		Mesh:     m,
+		Store:    st,
+		cancel:   cancel,
+	}
+
+	mgr.mu.Lock()
+	mgr.networks[netID] = net
+	mgr.order = append(mgr.order, netID)
+	mgr.mu.Unlock()
+
+	log.Printf("netmgr: joining network by hash id=%s peer=%s", netID, derived.PeerID().Short())
+
+	if mgr.cfg.AnchorURL != "" {
+		go func() {
+			anchor.RunByHash(ctx, mgr.cfg.AnchorURL, netHash64, derived, m)
+			log.Printf("netmgr: left network %s", netID)
+		}()
+	}
+
+	mgr.emit(proto.IpcMessage{
+		Type:        proto.EvtNetworkJoined,
+		NetworkID:   netID,
+		NetworkName: netID,
+		LocalPeer:   peerPtr(derived.PeerInfo()),
+		ShareDir:    m.ShareDir,
+	})
+
+	return netID, nil
+}
+
 // Leave cancels a network context by ID. Closes its store.
 func (mgr *Manager) Leave(netID string) {
 	mgr.mu.Lock()