fix: enable mobile diff view when no diff is preselected

Author: Dimillian

src/App.tsx

@@ -1933,6 +1933,7 @@ function MainApp() {
     gitStatus,
     fileStatus,
     perFileDiffGroups,
+    hasActiveGitDiffs: activeDiffs.length > 0,
     selectedDiffPath,
     diffScrollRequestId,
     onSelectDiff: handleSelectDiff,
@@ -2134,9 +2135,17 @@ function MainApp() {
       setCenterMode("chat");
     },
     onShowSelectedDiff: () => {
-      if (!selectedDiffPath) {
+      const fallbackPath =
+        selectedDiffPath ?? activeDiffs[0]?.path;
+
+      if (!fallbackPath) {
         return;
       }
+
+      if (!selectedDiffPath) {
+        setSelectedDiffPath(fallbackPath);
+      }
+
       setCenterMode("diff");
       if (isPhone) {
         setActiveTab("git");

src/features/layout/components/PhoneLayout.tsx

@@ -65,19 +65,17 @@ export function PhoneLayout({
       {activeTab === "git" && (
         <div className="compact-panel">
           {!activeWorkspace && compactEmptyGitNode}
-          {activeWorkspace && showGitDetail && (
-            <>
-              {compactGitBackNode}
-              <div className="compact-git-viewer">{gitDiffViewerNode}</div>
-            </>
-          )}
-          {activeWorkspace && !showGitDetail && (
+          {activeWorkspace && (
             <>
               <MainTopbar leftNode={topbarLeftNode} className="compact-topbar" />
               {compactGitBackNode}
-              <div className="compact-git">
-                <div className="compact-git-list">{gitDiffPanelNode}</div>
-              </div>
+              {showGitDetail ? (
+                <div className="compact-git-viewer">{gitDiffViewerNode}</div>
+              ) : (
+                <div className="compact-git">
+                  <div className="compact-git-list">{gitDiffPanelNode}</div>
+                </div>
+              )}
             </>
           )}
         </div>

src/features/layout/hooks/layoutNodes/buildSecondaryNodes.tsx

@@ -94,7 +94,7 @@ export function buildSecondaryNodes(options: LayoutNodesOptions): SecondaryLayou
         type="button"
         className={`compact-git-switch-button${compactGitDiffActive ? " active" : ""}`}
         onClick={options.onShowSelectedDiff}
-        disabled={!options.selectedDiffPath}
+        disabled={!options.hasActiveGitDiffs}
       >
         Diff
       </button>

src/features/layout/hooks/layoutNodes/types.ts

@@ -260,6 +260,7 @@ export type LayoutNodesOptions = {
   fileStatus: string;
   perFileDiffGroups: PerFileDiffGroup[];
   selectedDiffPath: string | null;
+  hasActiveGitDiffs: boolean;
   diffScrollRequestId: number;
   onSelectDiff: (path: string) => void;
   onSelectPerFileDiff: (path: string) => void;