Merge nucleic/clever-dewy-koala-vizm into dev

Sources/NucleicApp/ChatInputField.swift

@@ -127,6 +127,8 @@ struct ChatInputField: NSViewRepresentable {
         scroll.hasVerticalScroller = true
         scroll.hasHorizontalScroller = false
         scroll.autohidesScrollers = true
+        // Overlay from the start; the override above keeps AppKit from switching it back.
+        scroll.scrollerStyle = .overlay
 
         context.coordinator.textView = textView
         context.coordinator.scrollView = scroll
@@ -250,6 +252,22 @@ struct ChatInputField: NSViewRepresentable {
 final class HeightTrackingScrollView: NSScrollView {
     var onLayout: (() -> Void)?
 
+    /// Force overlay-style scrollers, rejecting the system's legacy style ("Show scroll
+    /// bars: Always", common with a mouse attached). A legacy scroller consumes layout
+    /// width when it appears, which re-wraps the text one line taller, which grows the
+    /// fitted height, which makes the content fit so the auto-hiding scroller disappears,
+    /// which widens the text back, re-wraps it shorter, shrinks the height, and brings the
+    /// scroller back — an endless oscillation that reads as the floating (⌘N/⌘⇧N) composer
+    /// bouncing/creeping downward with its text squashed (the sheet window resizes with
+    /// every cycle), and as a subtler jitter in the inline composers. Overlay scrollers
+    /// take no layout width, so scroller visibility can never feed back into text wrap.
+    /// AppKit re-applies the user's preferred style after init and on preference changes
+    /// through this setter, so coercing it here keeps the style pinned for good.
+    override var scrollerStyle: NSScroller.Style {
+        get { super.scrollerStyle }
+        set { _ = newValue; super.scrollerStyle = .overlay }
+    }
+
     override func layout() {
         super.layout()
         onLayout?()

Sources/NucleicApp/NewChatComposer.swift

@@ -95,7 +95,7 @@ struct NewChatComposer: View {
                 composerCore
             }
             .padding(20)
-            .frame(width: 640)
+            .frame(width: 720)
             // The destination selector replaced the Cancel button on the project row, so carry
             // Cancel's Escape-to-dismiss here (clicking outside the panel also dismisses — see
             // NewChatComposerSheet).