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.dart

@@ -890,23 +890,101 @@ abstract class AppLocalizations {
   /// **'Could not load README.'**
   String get storeDocsErrorGeneric;
 
-  /// No description provided for @storeFederationNudgeTitle.
+  /// No description provided for @storeSourceLabel.
   ///
   /// In en, this message translates to:
-  /// **'Want more capabilities?'**
-  String get storeFederationNudgeTitle;
+  /// **'Source'**
+  String get storeSourceLabel;
 
-  /// No description provided for @storeFederationNudgeBody.
+  /// No description provided for @storeSourceAll.
   ///
   /// In en, this message translates to:
-  /// **'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 storeFederationNudgeBody;
+  /// **'All sources'**
+  String get storeSourceAll;
 
-  /// No description provided for @storeFederationNudgeButton.
+  /// No description provided for @storeSourceNative.
   ///
   /// In en, this message translates to:
-  /// **'Open Settings'**
-  String get storeFederationNudgeButton;
+  /// **'Native'**
+  String get storeSourceNative;
+
+  /// No description provided for @storeSourceMcp.
+  ///
+  /// In en, this message translates to:
+  /// **'MCP'**
+  String get storeSourceMcp;
+
+  /// No description provided for @storeSourceN8n.
+  ///
+  /// In en, this message translates to:
+  /// **'n8n'**
+  String get storeSourceN8n;
+
+  /// No description provided for @storeProvenanceNative.
+  ///
+  /// In en, this message translates to:
+  /// **'native'**
+  String get storeProvenanceNative;
+
+  /// No description provided for @storeProvenanceMcp.
+  ///
+  /// In en, this message translates to:
+  /// **'mcp · {provider}'**
+  String storeProvenanceMcp(String provider);
+
+  /// No description provided for @storeProvenanceN8n.
+  ///
+  /// In en, this message translates to:
+  /// **'n8n · {provider}'**
+  String storeProvenanceN8n(String provider);
+
+  /// No description provided for @storeRecommendedTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'Add a public source — one click'**
+  String get storeRecommendedTitle;
+
+  /// No description provided for @storeRecommendedBody.
+  ///
+  /// In en, this message translates to:
+  /// **'Curated MCP servers reachable over HTTPS. No subprocess, no API key, no Node. Federated capabilities appear in the store immediately.'**
+  String get storeRecommendedBody;
+
+  /// No description provided for @storeRecommendedAddTooltip.
+  ///
+  /// In en, this message translates to:
+  /// **'Add and discover'**
+  String get storeRecommendedAddTooltip;
+
+  /// No description provided for @storeRecommendedAdding.
+  ///
+  /// In en, this message translates to:
+  /// **'Adding…'**
+  String get storeRecommendedAdding;
+
+  /// No description provided for @storeRecommendedDeepWikiTagline.
+  ///
+  /// In en, this message translates to:
+  /// **'GitHub repo documentation search (AI-powered)'**
+  String get storeRecommendedDeepWikiTagline;
+
+  /// No description provided for @storeRecommendedSemgrepTagline.
+  ///
+  /// In en, this message translates to:
+  /// **'Security scanning for code vulnerabilities'**
+  String get storeRecommendedSemgrepTagline;
+
+  /// No description provided for @storeProviderAddedToast.
+  ///
+  /// In en, this message translates to:
+  /// **'Added {name} — {n} federated {n, plural, =1{capability} other{capabilities}}.'**
+  String storeProviderAddedToast(String name, int n);
+
+  /// No description provided for @storeProviderAddFailed.
+  ///
+  /// In en, this message translates to:
+  /// **'Could not add {name}: {error}'**
+  String storeProviderAddFailed(String name, String error);
 
   /// No description provided for @auditTitle.
   ///