Trigger folder access prompts in permission checks; add lead welcome

mac/Sources/Byre/Chat.swift

@@ -6,6 +6,26 @@ enum ChatKind: Equatable {
     case task(String?)
 }
 
+#if os(macOS)
+private let leadPlaces = "Tasks open on the right; [switch between them](byre-app://switcher) with ⌘K. Their questions, finished work and reviews wait for you there."
+private let leadSettings = "pick the default model for new tasks, turn on notifications, and check this Mac's permissions so agents can see and control it and read your Desktop, Documents and Downloads. The [Server](byre-app://tab?name=server) tab checks the same for the server's agents."
+#else
+private let leadPlaces = "Tasks live in the Tasks tab, with the ones waiting on you marked; [find or start one](byre-app://switcher) any time."
+private let leadSettings = "pick the default model for new tasks, turn on notifications, and choose this server's window color."
+#endif
+
+private let leadMore = "As you work, the lead keeps [Notes](byre-app://tab?name=notes) on how you like things done, [Workflows](byre-app://tab?name=workflows) run several agents on one job, such as a review, and [Status](byre-app://tab?name=status) shows the turns running now and how much of each vendor's limits you've used."
+
+private let leadWelcome = """
+**Welcome to byre.** This is your lead, the agent you talk to about all your work. Tell it what you want done and it starts tasks: each one is an agent working on its own branch of a project, which you merge when you're happy with it. Ask it to add a project first, giving the path of a git repository on the server.
+
+\(leadPlaces)
+
+\(leadMore)
+
+Start in [Settings](byre-app://tab?name=settings): \(leadSettings)
+"""
+
 struct AttentionGroup: Identifiable {
     let id: String
     let label: String
@@ -157,6 +177,10 @@ final class ChatModel {
         kind == .lead && store.leadHasOlder()
     }
 
+    var welcome: Bool {
+        kind == .lead && !loading && !hasOlder && builder.root.rows.isEmpty && builder.pending.isEmpty
+    }
+
     func start() {
         if started {
             return
@@ -790,6 +814,10 @@ private struct TranscriptScroll: View {
                         PendingView(pending: p, model: model)
                             .padding(.top, 12)
                     }
+                    if model.welcome {
+                        MarkdownView(blocks: parseMarkdown(leadWelcome))
+                            .padding(.top, 12)
+                    }
                 }
             }
             .scrollTargetLayout()