feat(studio): clearer store + channel switcher + approvals & welcome polish

- store: repair the filter dialog crash (a Spacer lived directly in
  AlertDialog.actions, which is an OverflowBar, not a Flex — it threw
  and rendered a broken dialog). Buttons now sit in a Row.
- store: promote the module-store manager from a bare icon to a
  labelled 'Add store' button, and fully localize the dialog (DE/EN).
- store: add a curated 'Suggested stores' shelf with one-click
  add/remove (first entry: Recl∆Im). Each suggestion is probed for
  reachability and shows 'not available yet' until its index is
  published, instead of failing only on click. Fail-open on network
  errors so a transient hiccup never hides a real store.
- sidebar: the channel pill is now a one-click channel switcher
  (menu with per-channel running state + active check; switching
  writes ~/.chain/current-channel, restarts the daemon, and Studio
  repoints to the new channel).
- approvals: lead the card with the human prompt ('what am I
  releasing?') and demote the flow/step id to a metadata line; clear
  fallback when the step left the prompt empty.
- welcome: tidy the docs grid into equal-height paired rows with a
  full-width trailing card for the odd one out.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/main.dart

@@ -5,6 +5,7 @@
 
 import 'dart:async';
 
+import 'package:chain_client_sdk/chain_client_sdk.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
@@ -931,47 +932,200 @@ class _SidebarState extends State<_Sidebar>
   }
 }
 
-/// Active-channel indicator. Click to open Settings (where the
-/// operator can switch). Color-coded so production deployments
-/// look visibly different from local-dev — the kind of thing
-/// you want to see before clicking "Clear log".
-class _ChannelPill extends StatelessWidget {
-  final String channel;
-  const _ChannelPill({required this.channel});
-
-  Color _accent(ColorScheme cs) {
-    switch (channel) {
-      case 'production':
-        // "Live & healthy", not an error — red here read as a fault.
-        return ChainColors.success;
-      case 'beta':
-        return ChainColors.warning;
-      case 'dev':
-        return cs.primary;
-      case 'local':
-      default:
-        return cs.onSurfaceVariant;
-    }
+/// Accent colour for a channel name. Color-coded so production
+/// deployments look visibly different from local-dev — the kind of
+/// thing you want to see before clicking "Clear log". Shared by the
+/// pill, the collapsed chip, and the switch menu so all three stay
+/// in lockstep.
+Color _channelAccent(String channel, ColorScheme cs) {
+  switch (channel) {
+    case 'production':
+      // "Live & healthy", not an error — red here read as a fault.
+      return ChainColors.success;
+    case 'beta':
+      return ChainColors.warning;
+    case 'dev':
+      return cs.primary;
+    case 'local':
+    default:
+      return cs.onSurfaceVariant;
   }
+}
 
-  IconData get _icon {
-    switch (channel) {
-      case 'production':
-        return Icons.shield_outlined;
-      case 'beta':
-        return Icons.science_outlined;
-      case 'dev':
-        return Icons.bolt_outlined;
-      case 'local':
-      default:
-        return Icons.home_work_outlined;
-    }
+IconData _channelIcon(String channel) {
+  switch (channel) {
+    case 'production':
+      return Icons.shield_outlined;
+    case 'beta':
+      return Icons.science_outlined;
+    case 'dev':
+      return Icons.bolt_outlined;
+    case 'local':
+    default:
+      return Icons.home_work_outlined;
   }
+}
+
+/// Open the channel-switch menu anchored at [anchor]'s widget, then
+/// act on the selection. Switching runs `chain channel switch`
+/// (writes `~/.chain/current-channel` AND restarts that channel's
+/// daemon), then repoints Studio's wire at the new channel so the
+/// connection follows the switch immediately — the 5s health poll
+/// then refreshes the active-channel label. Shared by the expanded
+/// pill and the collapsed chip.
+///
+/// Falls back to the full Settings dialog when the hub is down (the
+/// snapshot RPC fails) so the operator can still pick + start a
+/// channel from there.
+Future<void> _showChannelSwitchMenu(BuildContext anchor, String current) async {
+  // Capture everything that reads from the context up front, before
+  // any await — these stay valid for the rest of the flow and keep
+  // the analyzer happy about context-across-async-gaps.
+  final l = AppLocalizations.of(anchor)!;
+  final messenger = ScaffoldMessenger.of(anchor);
+  final box = anchor.findRenderObject() as RenderBox?;
+  final overlay = Overlay.of(anchor).context.findRenderObject() as RenderBox?;
+  if (box == null || overlay == null) return;
+
+  ChannelStatusSnapshot snap;
+  try {
+    snap = await HubService.instance.channelStatus();
+  } catch (_) {
+    if (anchor.mounted) ChainSettingsDialog.show(anchor);
+    return;
+  }
+  if (!anchor.mounted) return;
+
+  // Anchor the menu to the pill's top edge, opening downward.
+  final origin = box.localToGlobal(Offset.zero, ancestor: overlay);
+  final position = RelativeRect.fromLTRB(
+    origin.dx,
+    origin.dy + box.size.height,
+    overlay.size.width - origin.dx - box.size.width,
+    0,
+  );
+
+  const settingsValue = '__settings__';
+  final selected = await showMenu<String>(
+    context: anchor,
+    position: position,
+    items: [
+      for (final ch in snap.channels)
+        PopupMenuItem<String>(
+          value: ch.name,
+          child: _ChannelMenuItem(channel: ch, active: ch.name == snap.active),
+        ),
+      const PopupMenuDivider(),
+      PopupMenuItem<String>(
+        value: settingsValue,
+        child: Row(
+          children: [
+            Icon(
+              Icons.settings_outlined,
+              size: 16,
+              color: Theme.of(anchor).colorScheme.onSurfaceVariant,
+            ),
+            const SizedBox(width: ChainSpace.sm),
+            Text(l.searchSettingsLabel),
+          ],
+        ),
+      ),
+    ],
+  );
+  if (selected == null || !anchor.mounted) return;
+  if (selected == settingsValue) {
+    ChainSettingsDialog.show(anchor);
+    return;
+  }
+  if (selected == snap.active) return;
+
+  final r = await SystemActions.chainChannelSwitch(selected);
+  if (!anchor.mounted) return;
+  if (!r.ok) {
+    showFaiProcessError(
+      anchor,
+      'channel.switch',
+      r.stdout,
+      r.stderr,
+      title: l.channelSwitchFailed(''),
+    );
+    return;
+  }
+  // Repoint Studio at the freshly-restarted channel daemon. persist:
+  // false keeps launch-time auto-discovery following ~/.chain, so the
+  // CLI pointer remains the single source of truth.
+  final target = snap.channels.firstWhere(
+    (c) => c.name == selected,
+    orElse: () =>
+        ChannelInfo(name: selected, port: 50051, running: true, endpoint: ''),
+  );
+  try {
+    await HubService.instance.reconnect(
+      HubEndpoint(host: '127.0.0.1', port: target.port),
+      persist: false,
+    );
+  } catch (_) {/* health poll will retry */}
+  if (anchor.mounted) {
+    messenger.showSnackBar(
+      SnackBar(content: Text(l.channelSwitchOk(selected))),
+    );
+  }
+}
+
+/// One row in the channel-switch menu: accent icon, name, a
+/// running/stopped dot, and a check on the active channel.
+class _ChannelMenuItem extends StatelessWidget {
+  final ChannelInfo channel;
+  final bool active;
+  const _ChannelMenuItem({required this.channel, required this.active});
 
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
-    final accent = _accent(theme.colorScheme);
+    final accent = _channelAccent(channel.name, theme.colorScheme);
+    return Row(
+      children: [
+        Icon(_channelIcon(channel.name), size: 15, color: accent),
+        const SizedBox(width: ChainSpace.sm),
+        Text(
+          channel.name,
+          style: ChainTheme.mono(
+            size: 12,
+            weight: FontWeight.w600,
+            color: theme.colorScheme.onSurface,
+          ),
+        ),
+        const SizedBox(width: ChainSpace.sm),
+        Container(
+          width: 7,
+          height: 7,
+          decoration: BoxDecoration(
+            color: channel.running
+                ? ChainColors.success
+                : theme.colorScheme.onSurfaceVariant.withValues(alpha: 0.4),
+            shape: BoxShape.circle,
+          ),
+        ),
+        const Spacer(),
+        if (active)
+          Icon(Icons.check, size: 16, color: theme.colorScheme.primary),
+      ],
+    );
+  }
+}
+
+/// Active-channel indicator + switcher. Click to open the channel
+/// menu and switch directly (writes `~/.chain/current-channel` and
+/// restarts the daemon). Color-coded so production stays
+/// unmistakeable.
+class _ChannelPill extends StatelessWidget {
+  final String channel;
+  const _ChannelPill({required this.channel});
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final accent = _channelAccent(channel, theme.colorScheme);
     final l = AppLocalizations.of(context)!;
     return Tooltip(
       message: l.sidebarChannelTooltip,
@@ -980,7 +1134,7 @@ class _ChannelPill extends StatelessWidget {
         borderRadius: BorderRadius.circular(ChainRadius.sm),
         child: InkWell(
           borderRadius: BorderRadius.circular(ChainRadius.sm),
-          onTap: () => ChainSettingsDialog.show(context),
+          onTap: () => _showChannelSwitchMenu(context, channel),
           child: Container(
             padding: const EdgeInsets.symmetric(
               horizontal: ChainSpace.sm,
@@ -993,7 +1147,7 @@ class _ChannelPill extends StatelessWidget {
             child: Row(
               mainAxisSize: MainAxisSize.min,
               children: [
-                Icon(_icon, size: 11, color: accent),
+                Icon(_channelIcon(channel), size: 11, color: accent),
                 const SizedBox(width: 4),
                 Text(
                   channel,
@@ -1003,6 +1157,8 @@ class _ChannelPill extends StatelessWidget {
                     color: accent,
                   ),
                 ),
+                const SizedBox(width: 2),
+                Icon(Icons.arrow_drop_down, size: 12, color: accent),
               ],
             ),
           ),
@@ -1054,21 +1210,6 @@ class _CollapsedChannelChip extends StatelessWidget {
   final String channel;
   const _CollapsedChannelChip({required this.channel});
 
-  Color _accent(ColorScheme cs) {
-    switch (channel) {
-      case 'production':
-        // "Live & healthy", not an error — red here read as a fault.
-        return ChainColors.success;
-      case 'beta':
-        return ChainColors.warning;
-      case 'dev':
-        return cs.primary;
-      case 'local':
-      default:
-        return cs.onSurfaceVariant;
-    }
-  }
-
   String get _letter {
     if (channel.isEmpty) return '·';
     return channel.substring(0, 1).toUpperCase();
@@ -1077,18 +1218,29 @@ class _CollapsedChannelChip extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
-    final accent = _accent(theme.colorScheme);
-    return Container(
-      width: 18,
-      height: 18,
-      decoration: BoxDecoration(
-        shape: BoxShape.circle,
-        border: Border.all(color: accent.withValues(alpha: 0.55)),
-      ),
-      alignment: Alignment.center,
-      child: Text(
-        _letter,
-        style: ChainTheme.mono(size: 10, weight: FontWeight.w700, color: accent),
+    final accent = _channelAccent(channel, theme.colorScheme);
+    return MouseRegion(
+      cursor: SystemMouseCursors.click,
+      child: GestureDetector(
+        behavior: HitTestBehavior.opaque,
+        onTap: () => _showChannelSwitchMenu(context, channel),
+        child: Container(
+          width: 18,
+          height: 18,
+          decoration: BoxDecoration(
+            shape: BoxShape.circle,
+            border: Border.all(color: accent.withValues(alpha: 0.55)),
+          ),
+          alignment: Alignment.center,
+          child: Text(
+            _letter,
+            style: ChainTheme.mono(
+              size: 10,
+              weight: FontWeight.w700,
+              color: accent,
+            ),
+          ),
+        ),
       ),
     );
   }