refactor: fold single-consumer helper types into their owners

Consolidate small single-purpose types into the files that own them:
StreamResult into StreamAnalyzer, the Planning context records into
PlanningSessionContext, PrimeClock/PrimeSchedulerOptions into PrimeScheduler,
AgentMcpTools into LifecycleMcpTools, the locator subclasses into
InstallArtifactLocator, LogLineViewModel into DetailsIslandViewModel,
RepoImportItemViewModel into its modal, and StepViewModel into InstallPageViewModel.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ClaudeDo.Worker/Prime/PrimeScheduler.cs

@@ -5,6 +5,17 @@ using Microsoft.Extensions.Hosting;
 
 namespace ClaudeDo.Worker.Prime;
 
+public sealed class PrimeClock : IPrimeClock
+{
+    public DateTimeOffset Now => DateTimeOffset.Now;
+}
+
+public sealed record PrimeSchedulerOptions(TimeSpan CatchUpWindow)
+{
+    public static PrimeSchedulerOptions Default { get; } =
+        new(TimeSpan.FromMinutes(30));
+}
+
 public sealed class PrimeScheduler : BackgroundService
 {
     private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;