Preserve detail navigation origin (#66)

TESTING.md

@@ -247,9 +247,17 @@ source update are published, and installs or updates Gotcha through AltStore PAL
       first activity-feed page without requiring a manual pull-up; the empty
       state appears only after every available page has been checked.
 - [ ] Tap repository, issue, pull-request, and commit activity. Each opens the
-      matching native tab and destination.
+      matching destination on the Home navigation stack. The navigation-bar
+      Back button and left-edge interactive swipe return directly to Home.
 - [ ] Non-linkable server activity does not navigate or appear tappable.
 
+## Milestone navigation
+
+- [ ] Open a milestone, then open one of its issues and one of its pull
+      requests. For each detail, the navigation-bar Back button and left-edge
+      interactive swipe return directly to that milestone, preserving its
+      rows and scroll position.
+
 ## Home-screen widgets
 
 - [ ] Upgrade over a build with an existing server. Launch Gotcha once, then

ios/Sources/AppContext.swift

@@ -96,10 +96,10 @@ final class AppContext {
     }
 
     func route(_ activity: ActivityRow) {
+        let navigation = navigationControllers[0]
         switch activity.target {
         case .repository:
-            tabs.selectedIndex = 1
-            navigationControllers[1].pushViewController(
+            navigation.pushViewController(
                 IssuesViewController(
                     context: self,
                     owner: activity.owner,
@@ -108,8 +108,7 @@ final class AppContext {
                 animated: true
             )
         case .issue:
-            tabs.selectedIndex = 1
-            navigationControllers[1].pushViewController(
+            navigation.pushViewController(
                 IssueViewController(
                     context: self,
                     owner: activity.owner,
@@ -119,8 +118,7 @@ final class AppContext {
                 animated: true
             )
         case .pullRequest:
-            tabs.selectedIndex = 3
-            navigationControllers[3].pushViewController(
+            navigation.pushViewController(
                 PullViewController(
                     context: self,
                     owner: activity.owner,
@@ -130,8 +128,7 @@ final class AppContext {
                 animated: true
             )
         case .commit:
-            tabs.selectedIndex = 2
-            navigationControllers[2].pushViewController(
+            navigation.pushViewController(
                 FilesViewController(
                     context: self,
                     owner: activity.owner,