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/Runner/StreamAnalyzer.cs

@@ -2,6 +2,17 @@ using System.Text.Json;
 
 namespace ClaudeDo.Worker.Runner;
 
+public sealed class StreamResult
+{
+    public string? ResultMarkdown { get; set; }
+    public string? StructuredOutputJson { get; set; }
+    public string? SessionId { get; set; }
+    public int TurnCount { get; set; }
+    public int TokensIn { get; set; }
+    public int TokensOut { get; set; }
+    public int ApiRetryCount { get; set; }
+}
+
 public sealed class StreamAnalyzer
 {
     private string? _resultMarkdown;