added more anomations

Sources/Shared/UI/Components/MessageBubbleEntrance.swift

@@ -0,0 +1,87 @@
+import SwiftUI
+
+/// Messages-style entrance for chat rows.
+///
+/// Opening a conversation reveals its first page as a bottom-up cascade
+/// (`.cascade`), and a row appended while the timeline is already rendered
+/// springs out of the composer's send control when outgoing (`.launch`).
+/// Everything else stays `.settled`, which keeps history scrolling, reactions
+/// and selection updates free of animation.
+struct MessageBubbleEntrance: ViewModifier {
+    enum Mode: Equatable {
+        case settled
+        case cascade(delay: TimeInterval)
+        case launch(outgoing: Bool)
+
+        var isSettled: Bool {
+            if case .settled = self { return true }
+            return false
+        }
+    }
+
+    let mode: Mode
+
+    // A settled row must never pass through an invisible frame, so only the
+    // rows that actually animate start hidden.
+    @State private var isRevealed: Bool
+    @State private var hasStarted = false
+
+    init(mode: Mode) {
+        self.mode = mode
+        _isRevealed = State(initialValue: mode.isSettled)
+    }
+
+    func body(content: Content) -> some View {
+        content
+            .opacity(isRevealed ? 1 : 0)
+            .scaleEffect(isRevealed ? 1 : displacedScale, anchor: scaleAnchor)
+            .offset(y: isRevealed ? 0 : displacedRise)
+            .onAppear(perform: reveal)
+    }
+
+    /// Outgoing bubbles shrink toward the trailing bottom corner, where the
+    /// composer's send control sits; incoming ones grow from their own edge.
+    private var displacedScale: CGFloat {
+        switch mode {
+        case .settled, .cascade:
+            return ChatMessageEntrancePolicy.entranceScale
+        case .launch(let outgoing):
+            return outgoing
+                ? ChatMessageEntrancePolicy.sendScale
+                : ChatMessageEntrancePolicy.receiveScale
+        }
+    }
+
+    private var scaleAnchor: UnitPoint {
+        if case .launch(let outgoing) = mode, outgoing { return .bottomTrailing }
+        return .bottom
+    }
+
+    private var displacedRise: CGFloat {
+        switch mode {
+        case .settled, .cascade:
+            return ChatMessageEntrancePolicy.entranceRise
+        case .launch(let outgoing):
+            return outgoing
+                ? ChatMessageEntrancePolicy.sendRise
+                : ChatMessageEntrancePolicy.receiveRise
+        }
+    }
+
+    private func reveal() {
+        guard !hasStarted else { return }
+        hasStarted = true
+        guard !isRevealed else { return }
+        let delay: TimeInterval
+        if case .cascade(let cascadeDelay) = mode {
+            delay = cascadeDelay
+        } else {
+            delay = 0
+        }
+        withAnimation(
+            ChatMessageEntrancePolicy.appendAnimation.delay(delay)
+        ) {
+            isRevealed = true
+        }
+    }
+}