feat(block2): Ğ1 — publish a Ğ1 address + 'Pay in Ğ1' in chat (levels 1-2)

The optional Ğ1 (free currency) integration, per g1-integration.md.
- Profile: an optional 'Ğ1 address' field, persisted locally and published in
  your NIP-01 kind:0 metadata (separate from the Nostr key).
- commons_core: UserProfile/ProfileTransport carry a 'g1' field (round-trip
  tested).
- Chat: when the peer published a Ğ1 address, a 'Pay in Ğ1' app-bar action opens
  their wallet (url_launcher) so value moves in the wallet, not the app — copies
  the address as a fallback. No payment rails in-app (sharing-model §4.3).

NOTE (vjrj): the wallet deep-link uses the Cesium web wallet as a universal
fallback; swap the URI in chat_screen._payG1 for the Ğ1nkgo/Ğecko scheme you
prefer. Analyzer clean (both packages); profile transport test covers g1.

apps/app_seeds/lib/ui/chat_screen.dart

@@ -1,7 +1,9 @@
 import 'dart:async';
 
 import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:url_launcher/url_launcher.dart';
 
 import '../i18n/strings.g.dart';
 import '../services/message_store.dart';
@@ -45,6 +47,7 @@ class _ChatScreenState extends State<ChatScreen> {
   TrustCubit? _trust;
   bool _loading = true;
   String? _peerName;
+  String? _peerG1;
   final _input = TextEditingController();
 
   @override
@@ -94,9 +97,15 @@ class _ChatScreenState extends State<ChatScreen> {
       unawaited(() async {
         try {
           final profile = await live.profile.fetch(widget.peerPubkey);
-          if (profile != null && profile.name.isNotEmpty && mounted) {
-            await widget.profileCache!.setName(widget.peerPubkey, profile.name);
-            setState(() => _peerName = profile.name);
+          if (profile != null && mounted) {
+            if (profile.name.isNotEmpty) {
+              await widget.profileCache!
+                  .setName(widget.peerPubkey, profile.name);
+            }
+            setState(() {
+              if (profile.name.isNotEmpty) _peerName = profile.name;
+              if (profile.g1.isNotEmpty) _peerG1 = profile.g1;
+            });
           }
         } catch (_) {
           // best effort
@@ -105,6 +114,30 @@ class _ChatScreenState extends State<ChatScreen> {
     }
   }
 
+  /// Opens the peer's Ğ1 wallet so you can pay them (Ğ1 is separate from the
+  /// Nostr key — this uses the address they published in their profile). Falls
+  /// back to copying the address if no wallet handles the link.
+  ///
+  /// NOTE: confirm the deep-link scheme for the target wallet (Ğ1nkgo / Ğecko /
+  /// Cesium) — this uses the Cesium web wallet as a universal fallback.
+  Future<void> _payG1() async {
+    final g1 = _peerG1;
+    if (g1 == null) return;
+    final messenger = ScaffoldMessenger.of(context);
+    final t = context.t;
+    final uri = Uri.parse('https://demo.cesium.app/#/app/wallet/$g1/');
+    var launched = false;
+    try {
+      launched = await launchUrl(uri, mode: LaunchMode.externalApplication);
+    } catch (_) {
+      launched = false;
+    }
+    if (!launched && mounted) {
+      await Clipboard.setData(ClipboardData(text: g1));
+      messenger.showSnackBar(SnackBar(content: Text(t.chat.g1Copied)));
+    }
+  }
+
   Future<void> _send() async {
     final cubit = _messages;
     if (cubit == null || _input.text.trim().isEmpty) return;
@@ -126,9 +159,19 @@ class _ChatScreenState extends State<ChatScreen> {
   Widget build(BuildContext context) {
     final messages = _messages;
     final trust = _trust;
+    final t = context.t;
     return Scaffold(
       appBar: AppBar(
         title: Text(_peerName ?? shortPubkey(widget.peerPubkey)),
+        actions: [
+          if (_peerG1 != null)
+            IconButton(
+              key: const Key('chat.payG1'),
+              icon: const Icon(Icons.payments_outlined),
+              tooltip: t.chat.payG1,
+              onPressed: _payG1,
+            ),
+        ],
       ),
       body: _loading || messages == null || trust == null
           ? const Center(child: CircularProgressIndicator())

apps/app_seeds/lib/ui/profile_screen.dart

@@ -30,6 +30,7 @@ class ProfileScreen extends StatefulWidget {
 class _ProfileScreenState extends State<ProfileScreen> {
   final _name = TextEditingController();
   final _about = TextEditingController();
+  final _g1 = TextEditingController();
   bool _loading = true;
   bool _saving = false;
 
@@ -42,6 +43,7 @@ class _ProfileScreenState extends State<ProfileScreen> {
   Future<void> _load() async {
     _name.text = await widget.profileStore.name();
     _about.text = await widget.profileStore.about();
+    _g1.text = await widget.profileStore.g1();
     if (mounted) setState(() => _loading = false);
   }
 
@@ -57,7 +59,8 @@ class _ProfileScreenState extends State<ProfileScreen> {
     final messenger = ScaffoldMessenger.of(context);
     final t = context.t;
     setState(() => _saving = true);
-    await widget.profileStore.save(name: _name.text, about: _about.text);
+    await widget.profileStore
+        .save(name: _name.text, about: _about.text, g1: _g1.text);
 
     // Best-effort publish to the network so peers see the name.
     final relays = await widget.settings.relayUrls();
@@ -67,6 +70,7 @@ class _ProfileScreenState extends State<ProfileScreen> {
         await session.profile.publish(
           name: _name.text.trim(),
           about: _about.text.trim(),
+          g1: _g1.text.trim(),
         );
         await session.close();
       } catch (_) {
@@ -82,6 +86,7 @@ class _ProfileScreenState extends State<ProfileScreen> {
   void dispose() {
     _name.dispose();
     _about.dispose();
+    _g1.dispose();
     super.dispose();
   }
 
@@ -116,6 +121,16 @@ class _ProfileScreenState extends State<ProfileScreen> {
                     helperText: t.profile.aboutHint,
                   ),
                 ),
+                const SizedBox(height: 16),
+                TextField(
+                  key: const Key('profile.g1'),
+                  controller: _g1,
+                  decoration: InputDecoration(
+                    labelText: t.profile.g1,
+                    helperText: t.profile.g1Hint,
+                    helperMaxLines: 2,
+                  ),
+                ),
                 const SizedBox(height: 24),
                 FilledButton(
                   key: const Key('profile.save'),