fix(mobile): keep conversation feed visible

apps/mobile/src/features/threads/ThreadRouteScreen.tsx

@@ -764,12 +764,12 @@ function ThreadRouteContent(
   const renderThreadRouteBody = (showActionControls: boolean) => (
     // A real flex host (not a fragment) keeps the thread body filling the
     // screen so the absolute composer overlay anchors to the true bottom.
-    <View className="flex-1 bg-screen">
+    <View testID="thread-conversation-surface" className="flex-1 bg-screen" style={{ flex: 1 }}>
       <ThreadGitControls {...threadGitControlProps} showActionControls={showActionControls} />
 
       <GitActionProgressOverlay progress={gitActionProgress} onDismiss={dismissGitActionResult} />
 
-      <View className="flex-1">
+      <View className="flex-1" style={{ flex: 1 }}>
         <ThreadDetailScreen
           selectedThread={selectedThreadWithDraftSettings ?? selectedThread}
           contentPresentation={contentPresentation}

apps/mobile/src/mobileSurfaceExistence.test.ts

@@ -0,0 +1,29 @@
+/**
+ * Existence contracts for mobile product surfaces that stack conflict
+ * resolution can accidentally leave structurally present but unrenderable.
+ */
+// @effect-diagnostics nodeBuiltinImport:off - existence contract reads source text on disk.
+import * as NodeFS from "node:fs";
+import * as NodePath from "node:path";
+import * as NodeURL from "node:url";
+import { describe, expect, it } from "vite-plus/test";
+
+const root = NodePath.dirname(NodeURL.fileURLToPath(import.meta.url));
+
+function readSrc(relativePath: string): string {
+  return NodeFS.readFileSync(NodePath.join(root, relativePath), "utf8");
+}
+
+describe("mobile surface existence (anti stack-drop)", () => {
+  it("keeps the conversation feed inside an explicit flex host", () => {
+    const threadRoute = readSrc("features/threads/ThreadRouteScreen.tsx");
+
+    expect(threadRoute).toContain('testID="thread-conversation-surface"');
+    expect(threadRoute).toMatch(
+      /testID="thread-conversation-surface"[\s\S]*?style=\{\{ flex: 1 \}\}/,
+    );
+    expect(threadRoute).toMatch(
+      /<View className="flex-1" style=\{\{ flex: 1 \}\}>[\s\S]*?<ThreadDetailScreen/,
+    );
+  });
+});