feat: animate the start-screen URL field

Use a scoped 250 ms fade and top-anchored scale transition with animated recent-row reflow. Respect Reduce Motion, preserve the fixed window size, and exercise native focus, draft retention and rapid reversals.

Checks/app-startup.swift

@@ -37,6 +37,8 @@ private enum WindowDragCheck {
     static var implementations: [(Method, IMP)] = []
     static var target: NSWindow?
     static var dragDepth = 0
+    static var urlWindowFrame = NSRect.zero
+    static let urlDraft = "https://www.youtube.com/watch?v=aqz-KE-bpKQ"
     static let names = ["video", "title", "playback padding", "play button", "volume slider",
                         "start whitespace", "start button", "start artwork", "URL text field",
                         "queue whitespace", "queue footer", "queue row", "queue button",
@@ -76,6 +78,17 @@ private enum WindowDragCheck {
         return nil
     }
 
+    static func clickStartURL(in window: NSWindow) {
+        for type in [NSEvent.EventType.leftMouseDown, .leftMouseUp] {
+            let event = NSEvent.mouseEvent(with: type, location: NSPoint(x: 400, y: 272),
+                modifierFlags: [], timestamp: ProcessInfo.processInfo.systemUptime,
+                windowNumber: window.windowNumber, context: nil,
+                eventNumber: probe * 100 + phase * 2 + (type == .leftMouseDown ? 0 : 1),
+                clickCount: 1, pressure: type == .leftMouseDown ? 1 : 0)!
+            NSApp.postEvent(NSEvent(cgEvent: event.cgEvent!)!, atStart: false)
+        }
+    }
+
     static func point(in window: NSWindow) -> NSPoint? {
         let content = window.contentView!
         let w = content.bounds.width
@@ -150,11 +163,13 @@ private enum WindowDragCheck {
             model.setVolume(0)
             model.setPlayback(playing: false)
             window.makeKeyAndOrderFront(nil)
+            window.makeMain()
             NSApp.activate(ignoringOtherApps: true)
         }
         if phase == 0 {
-            guard NSApp.isActive, window.isKeyWindow else {
+            guard NSApp.isActive, window.isKeyWindow, window.isMainWindow else {
                 window.makeKeyAndOrderFront(nil)
+                window.makeMain()
                 NSApp.activate(ignoringOtherApps: true)
                 return
             }
@@ -162,13 +177,8 @@ private enum WindowDragCheck {
             switch probe {
             case 5: model.closeFile()
             case 8:
-                for type in [NSEvent.EventType.leftMouseDown, .leftMouseUp] {
+                urlWindowFrame = window.frame
-                    let event = NSEvent.mouseEvent(with: type, location: NSPoint(x: 400, y: 272),
+                clickStartURL(in: window)
-                        modifierFlags: [], timestamp: ProcessInfo.processInfo.systemUptime,
-                        windowNumber: window.windowNumber, context: nil, eventNumber: type == .leftMouseDown ? 1 : 2,
-                        clickCount: 1, pressure: type == .leftMouseDown ? 1 : 0)!
-                    NSApp.postEvent(NSEvent(cgEvent: event.cgEvent!)!, atStart: false)
-                }
             case 9:
                 model.open(fixtures.appendingPathComponent("cache.mp4"))
                 model.showsQueue = true
@@ -205,10 +215,37 @@ private enum WindowDragCheck {
             guard drags - previousDrags == expected else {
                 finish("\(names[probe]): expected \(expected) native drag requests, got \(drags - previousDrags)"); return
             }
+            if probe == 8 {
+                guard let editor = window.firstResponder as? NSTextView, editor.isFieldEditor else {
+                    finish("Revealing the URL field did not focus its editor"); return
+                }
+                editor.insertText(urlDraft, replacementRange: NSRange(location: NSNotFound, length: 0))
+                clickStartURL(in: window)
+                phase = 7
+                return
+            }
             probe += 1
             if probe == names.count { finish(); return }
             phase = 0
             return
+        } else if probe == 8 && phase == 7 {
+            guard (window.firstResponder as? NSTextView)?.isFieldEditor != true else {
+                finish("Collapsing the URL field retained keyboard focus"); return
+            }
+            clickStartURL(in: window) // Reverse the collapse before its animation completes.
+        } else if probe == 8 && phase == 8 {
+            guard let editor = window.firstResponder as? NSTextView, editor.isFieldEditor else { return }
+            guard editor.string == urlDraft else { finish("Reopening the URL field lost its draft"); return }
+            clickStartURL(in: window)
+        } else if probe == 8 && phase == 9 {
+            guard nativeView(in: window.contentView!, matching: { ($0 as? NSTextField)?.isEditable == true }) == nil else { return }
+            guard (window.firstResponder as? NSTextView)?.isFieldEditor != true,
+                  window.frame == urlWindowFrame, drags == previousDrags else {
+                finish("URL-field transitions retained focus, resized or dragged the start window"); return
+            }
+            probe += 1
+            phase = 0
+            return
         }
         phase += 1
     }

README.md

@@ -41,6 +41,8 @@ The start screen uses a fixed 640 × 400-point two-pane window: Terebi's identit
 
 Start-screen actions use 14-point text and begin 64 points below the top edge. Branding uses a 16-point app name and 12-point version; the drop hint uses 13-point text. Open actions have no idle fill; their background appears on hover or press.
 
+URL-field expansion and collapse use a 250 ms ease-in/out fade with a subtle top-anchored scale; recent rows move with the transition without resizing the window. Reduce Motion makes the change immediate. Hiding or rapidly toggling the field preserves its draft, and hiding releases keyboard focus.
+
 | Action | Default shortcut |
 | --- | --- |
 | Play / pause | Space or K |

Sources/App/TerebiApp.swift

@@ -2189,7 +2189,10 @@ private struct PlayerContent: View {
                     }
                     .buttonStyle(StartScreenButtonStyle())
                     .accessibilityLabel("Open YouTube URL…")
-                    if showsYouTubeInput { startURLInput.padding(.horizontal, 14) }
+                    if showsYouTubeInput {
+                        startURLInput.padding(.horizontal, 14)
+                            .transition(.opacity.combined(with: .scale(scale: 0.96, anchor: .top)))
+                    }
                     if let latest, let resumePosition {
                         Button { model.open(latest.url) } label: {
                             HStack(spacing: 8) {
@@ -2224,6 +2227,7 @@ private struct PlayerContent: View {
                             .padding(.top, 20)
                     }
                 }
+                .animation(reduceMotion ? nil : .easeInOut(duration: 0.25), value: showsYouTubeInput)
                 .font(.system(size: 14, weight: .medium))
                 .disabled(!model.canOpen)
                 .padding(.horizontal, size.width < 600 ? 14 : 30)

TODO.md

@@ -13,6 +13,7 @@
 - [x] make the window draggable (in all cases/view states) so long as a button/clickable element is not hovered.
     - scoped native background dragging across start/playback/queue/error/Cast/compact views, with passive loading/audio overlays passing input through; 20 native input-routing probes passed, including controls and row-reorder exclusions; physical pointer dragging and Cast-screen interaction still need manual verification
 - [ ] on the start screen:
-    - [ ] make the youtube url input field that appears when clicking the youtube button appear with a nice transition
+    - [x] make the youtube url input field that appears when clicking the youtube button appear with a nice transition
+        - 250 ms fade/scale with animated row reflow; native focus, draft-preservation and rapid-reversal checks passed, including an isolated Reduce Motion branch smoke check; animation feel still needs manual verification
     - [ ] change the youtube button to general streaming
 	    - we can figure out the stream and how to handle it from the url (i.e. if youtube url, handle as youtube stream; if miruro url, handle accordingly)