fix(canvas): float the workspace mode selector over the channel feed

packages/ui/src/features/canvas/components/ChannelFeedView.tsx

@@ -856,8 +856,10 @@ export function ChannelFeedView({
         <ChatMessageScrollerViewport ref={viewportRef}>
           {/* Horizontal padding is load-bearing: ThreadItem's actions float at
               the row's top-right corner (absolute, past the row edge). Without a
-              gutter they hug the scroll container and get clipped. */}
-          <ChatMessageScrollerContent className="mx-auto w-full gap-0 py-4">
+              gutter they hug the scroll container and get clipped. The deeper
+              bottom padding clears the composer's floating workspace-mode
+              selector, which hangs over the end of the feed. */}
+          <ChatMessageScrollerContent className="mx-auto w-full gap-0 pt-4 pb-10">
             {intro}
             {entries.map((entry, index) => {
               const previous = entries[index - 1];

packages/ui/src/features/canvas/components/ChannelHomeComposer.tsx

@@ -371,11 +371,13 @@ export const ChannelHomeComposer = forwardRef<
   const submitComposer = canvasArmed ? handleCanvasSubmit : submit;
 
   return (
-    <div className="flex w-full flex-col">
+    <div className="relative flex w-full flex-col">
       {/* Canvas generation always runs in the cloud, so the local/cloud pick
-          doesn't apply while canvas mode is armed. */}
+          doesn't apply while canvas mode is armed. The row floats over the feed,
+          and the trigger's own fill is translucent, so it carries an opaque
+          backdrop at the button's radius to stop messages showing through. */}
       {!canvasArmed && (
-        <div className="mb-2 flex items-center gap-2">
+        <div className="absolute bottom-full left-0 mb-2 flex items-center gap-2 rounded-sm bg-card">
           <WorkspaceModeSelect
             value={workspaceMode}
             onChange={setWorkspaceMode}

packages/ui/src/features/canvas/components/WebsiteChannelHome.tsx

@@ -303,7 +303,7 @@ export function WebsiteChannelHome({ channelId }: { channelId: string }) {
           onOpenTask={handleOpenTask}
           onOpenThread={handleOpenThread}
         />
-        <div className="mx-auto w-full px-4 pb-4">
+        <div className="mx-auto w-full px-4 pt-2 pb-4">
           <ChannelHomeComposer
             ref={composerRef}
             channelId={channelId}