feat(studio): store-side source filter, provenance pills, one-click recommended sources (v0.29.0)

The Store is now the centre of capability discovery — provider
configuration moves out of Settings into the Store itself.
Three changes work together:

1. Source filter chips next to the existing status chips:
   All sources / Native / MCP / n8n. Applied client-side after
   the hub returns results so toggling is instant. The result
   count and the "Clear filters" reset both account for the
   source filter too.

2. Per-card provenance pill (`_ProvenancePill`): shows whether
   each entry is native, mcp · <provider>, or n8n · <provider>
   so the operator can triage the source at a glance — same
   role the "verified" badge plays in commercial app stores.

3. `_RecommendedSourcesStrip` replaces the older
   `_FederationNudge`. Renders curated public MCP servers
   (DeepWiki, Semgrep) as one-click cards with an inline
   `[+ Add]` button — no Settings detour, no form. Both servers
   are HTTPS Streamable-HTTP, no API key, no subprocess.
   Useful AI was considered but its 340+ tools would drown the
   index — kept out of the curated list. The strip auto-hides
   the moment any federated entry exists.

Removed the now-orphaned storeFederationNudge* ARB keys.

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

lib/l10n/app_localizations_en.dart

@@ -489,14 +489,69 @@ class AppLocalizationsEn extends AppLocalizations {
   String get storeDocsErrorGeneric => 'Could not load README.';
 
   @override
-  String get storeFederationNudgeTitle => 'Want more capabilities?';
+  String get storeSourceLabel => 'Source';
 
   @override
-  String get storeFederationNudgeBody =>
-      'Configure an MCP server or n8n endpoint in Settings → MCP Clients / N8N Endpoints. Discovered tools and workflows surface here as `mcp.<server>.<tool>` and `n8n.<endpoint>.<workflow>` capabilities — every Anthropic / community MCP server adds a handful at once.';
+  String get storeSourceAll => 'All sources';
 
   @override
-  String get storeFederationNudgeButton => 'Open Settings';
+  String get storeSourceNative => 'Native';
+
+  @override
+  String get storeSourceMcp => 'MCP';
+
+  @override
+  String get storeSourceN8n => 'n8n';
+
+  @override
+  String get storeProvenanceNative => 'native';
+
+  @override
+  String storeProvenanceMcp(String provider) {
+    return 'mcp · $provider';
+  }
+
+  @override
+  String storeProvenanceN8n(String provider) {
+    return 'n8n · $provider';
+  }
+
+  @override
+  String get storeRecommendedTitle => 'Add a public source — one click';
+
+  @override
+  String get storeRecommendedBody =>
+      'Curated MCP servers reachable over HTTPS. No subprocess, no API key, no Node. Federated capabilities appear in the store immediately.';
+
+  @override
+  String get storeRecommendedAddTooltip => 'Add and discover';
+
+  @override
+  String get storeRecommendedAdding => 'Adding…';
+
+  @override
+  String get storeRecommendedDeepWikiTagline =>
+      'GitHub repo documentation search (AI-powered)';
+
+  @override
+  String get storeRecommendedSemgrepTagline =>
+      'Security scanning for code vulnerabilities';
+
+  @override
+  String storeProviderAddedToast(String name, int n) {
+    String _temp0 = intl.Intl.pluralLogic(
+      n,
+      locale: localeName,
+      other: 'capabilities',
+      one: 'capability',
+    );
+    return 'Added $name — $n federated $_temp0.';
+  }
+
+  @override
+  String storeProviderAddFailed(String name, String error) {
+    return 'Could not add $name: $error';
+  }
 
   @override
   String get auditTitle => 'Audit';