feat(ui): DetailsIslandViewModel with agent state and log

Implements LogLineViewModel (LogKind enum + ClassName), full
DetailsIslandViewModel (editable title, notes, prompt, agent strip
fields, Log/Subtasks collections, Bind method, SendPromptCommand,
ApproveMergeCommand, StopCommand). Wires TaskMessageEvent for live log.
Updates Program.cs DI for new IDbContextFactory + WorkerClient deps.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Ui/ViewModels/Islands/LogLineViewModel.cs

@@ -0,0 +1,20 @@
+namespace ClaudeDo.Ui.ViewModels.Islands;
+
+public enum LogKind { Sys, Tool, Claude, Stdout, Stderr, Done, Msg }
+
+public sealed class LogLineViewModel
+{
+    public required LogKind Kind { get; init; }
+    public required string Text { get; init; }
+    public string ClassName => Kind switch
+    {
+        LogKind.Sys    => "log-sys",
+        LogKind.Tool   => "log-tool",
+        LogKind.Claude => "log-claude",
+        LogKind.Stdout => "log-stdout",
+        LogKind.Stderr => "log-stderr",
+        LogKind.Done   => "log-done",
+        LogKind.Msg    => "log-msg",
+        _              => "",
+    };
+}