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/pages/approvals.dart

@@ -527,6 +527,9 @@ class _ApprovalCard extends StatelessWidget {
       child: Column(
         crossAxisAlignment: CrossAxisAlignment.start,
         children: [
+          // Status row: selection + state + expiry. No flow id here —
+          // the headline below leads with WHAT is being asked, not the
+          // technical flow name.
           Row(
             children: [
               Checkbox(
@@ -540,15 +543,7 @@ class _ApprovalCard extends StatelessWidget {
                 tone: ChainPillTone.warning,
                 icon: Icons.pending_outlined,
               ),
-              const SizedBox(width: ChainSpace.sm),
-              Expanded(
-                child: Text(
-                  '${approval.flowName} › ${approval.stepId}',
-                  style: theme.textTheme.titleMedium?.copyWith(
-                    fontWeight: FontWeight.w600,
-                  ),
-                ),
-              ),
+              const Spacer(),
               if (approval.expiresAt != null)
                 ChainPill(
                   label: _expiresInLabel(context, approval.expiresAt!),
@@ -558,7 +553,38 @@ class _ApprovalCard extends StatelessWidget {
             ],
           ),
           const SizedBox(height: ChainSpace.lg),
-          Text(approval.prompt, style: theme.textTheme.bodyLarge),
+          // Headline = the human question the flow author wrote ("what
+          // am I approving"). Falls back to a clear sentence when the
+          // step left the prompt empty, so the card is never reduced to
+          // a cryptic flow id.
+          Text(
+            approval.prompt.trim().isEmpty
+                ? l.approvalsRequestFallback
+                : approval.prompt,
+            style: theme.textTheme.titleMedium?.copyWith(
+              fontWeight: FontWeight.w600,
+            ),
+          ),
+          const SizedBox(height: 4),
+          // Technical context, demoted to a small metadata line.
+          Row(
+            children: [
+              Icon(
+                Icons.account_tree_outlined,
+                size: 13,
+                color: theme.colorScheme.onSurfaceVariant,
+              ),
+              const SizedBox(width: 6),
+              Expanded(
+                child: Text(
+                  l.approvalsFlowStepMeta(approval.flowName, approval.stepId),
+                  style: theme.textTheme.bodySmall?.copyWith(
+                    color: theme.colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ),
+            ],
+          ),
           if (approval.payloadPreview != null) ...[
             const SizedBox(height: ChainSpace.md),
             Padding(