Add session filter to Activity view

Dropdown in the filter bar lets users scope activity to a single
session or view all. Sessions are labeled with their first user
message preview. Combines with the existing tool-kind filter.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scarf/scarf/Features/Activity/ViewModels/ActivityViewModel.swift

@@ -6,9 +6,20 @@ final class ActivityViewModel {
 
     var toolMessages: [HermesMessage] = []
     var filterKind: ToolKind?
+    var filterSessionId: String?
     var selectedEntry: ActivityEntry?
+    var sessionPreviews: [String: String] = [:]
     var isLoading = true
 
+    var availableSessions: [(id: String, label: String)] {
+        var seen = Set<String>()
+        return toolMessages.compactMap { message in
+            guard seen.insert(message.sessionId).inserted else { return nil }
+            let label = sessionPreviews[message.sessionId] ?? message.sessionId
+            return (id: message.sessionId, label: label)
+        }
+    }
+
     var filteredActivity: [ActivityEntry] {
         let entries = toolMessages.flatMap { message in
             message.toolCalls.map { call in
@@ -24,10 +35,11 @@ final class ActivityViewModel {
                 )
             }
         }
-        if let filterKind {
+        return entries.filter { entry in
-            return entries.filter { $0.kind == filterKind }
+            let kindOk = filterKind == nil || entry.kind == filterKind
+            let sessionOk = filterSessionId == nil || entry.sessionId == filterSessionId
+            return kindOk && sessionOk
         }
-        return entries
     }
 
     func load() async {
@@ -38,6 +50,7 @@ final class ActivityViewModel {
             return
         }
         toolMessages = await dataService.fetchRecentToolCalls(limit: 200)
+        sessionPreviews = await dataService.fetchSessionPreviews(limit: 200)
         isLoading = false
     }
 

scarf/scarf/Features/Activity/Views/ActivityView.swift

@@ -21,6 +21,7 @@ struct ActivityView: View {
     }
 
     private var filterBar: some View {
+        HStack(spacing: 12) {
             ScrollView(.horizontal, showsIndicators: false) {
                 HStack(spacing: 8) {
                     FilterChip(label: "All", isSelected: viewModel.filterKind == nil) {
@@ -32,10 +33,25 @@ struct ActivityView: View {
                         }
                     }
                 }
+            }
+            Divider()
+                .frame(height: 16)
+            Picker(selection: $viewModel.filterSessionId) {
+                Text("All Sessions").tag(String?.none)
+                Divider()
+                ForEach(viewModel.availableSessions, id: \.id) { session in
+                    Text(session.label)
+                        .lineLimit(1)
+                        .tag(String?.some(session.id))
+                }
+            } label: {
+                EmptyView()
+            }
+            .frame(maxWidth: 250)
+        }
         .padding(.horizontal)
         .padding(.vertical, 8)
     }
-    }
 
     private var activityList: some View {
         List(selection: Binding(