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.Ui/Services/InstallArtifactLocator.cs

@@ -1,5 +1,17 @@
 namespace ClaudeDo.Ui.Services;
 
+public sealed class InstallerLocator : InstallArtifactLocator
+{
+    protected override string Subdir => "uninstaller";
+    protected override string ExeName => "ClaudeDo.Installer.exe";
+}
+
+public sealed class WorkerLocator : InstallArtifactLocator
+{
+    protected override string Subdir => "worker";
+    protected override string ExeName => "ClaudeDo.Worker.exe";
+}
+
 /// <summary>
 /// Locates an executable inside a ClaudeDo install: walk up from the running
 /// directory to the folder containing install.json, otherwise read the

src/ClaudeDo.Ui/Services/InstallerLocator.cs

@@ -1,7 +0,0 @@
-namespace ClaudeDo.Ui.Services;
-
-public sealed class InstallerLocator : InstallArtifactLocator
-{
-    protected override string Subdir => "uninstaller";
-    protected override string ExeName => "ClaudeDo.Installer.exe";
-}

src/ClaudeDo.Ui/Services/WorkerLocator.cs

@@ -1,7 +0,0 @@
-namespace ClaudeDo.Ui.Services;
-
-public sealed class WorkerLocator : InstallArtifactLocator
-{
-    protected override string Subdir => "worker";
-    protected override string ExeName => "ClaudeDo.Worker.exe";
-}