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/anchor/client.go

@@ -60,7 +60,12 @@ func (s *peerSession) close() {
 // Run connects to anchorURL, joins networkName, and blocks handling signaling.
 // Reconnects automatically on disconnect. Cancel ctx to stop.
 func Run(ctx context.Context, anchorURL, networkName string, id *crypto.Identity, m *mesh.Mesh) {
-	netHash := hashNetName(networkName)
+	RunByHash(ctx, anchorURL, hashNetName(networkName), id, m)
+}
+
+// RunByHash is like Run but accepts the pre-computed full 64-char hex network hash
+// directly. Use this when joining by hash rather than by name.
+func RunByHash(ctx context.Context, anchorURL, netHash string, id *crypto.Identity, m *mesh.Mesh) {
 	for {
 		if err := runOnce(ctx, anchorURL, netHash, id, m); err != nil {
 			if ctx.Err() != nil {