feat(app): polish workspace tabs and changes

Size tabs from rendered labels and switch to horizontal overflow once minimum click targets are reached, keeping the add-tab action adjacent until it must remain fixed.

Make Changes an always-expanded document with an optional desktop navigation tree, keep Git actions in their platform-owned headers, remove pinned and inline split shortcuts, and place review tabs beside Changes.

packages/app/src/stores/panel-store/index.ts

@@ -79,7 +79,6 @@ export interface PanelState {
   explorerTab: ExplorerTab;
   explorerTabByCheckout: Record<string, ExplorerTab>;
   expandedPathsByWorkspace: Record<string, string[]>;
-  diffExpandedPathsByWorkspace: Record<string, string[]>;
   // Changes-view folder tree. Inverted semantics vs the fields above:
   // this stores COLLAPSED directory paths (empty = all folders expanded), keyed
   // by full uncompressed dir path, so folders default to expanded and new
@@ -111,7 +110,6 @@ export interface PanelState {
   setExplorerTab: (tab: ExplorerTab) => void;
   setExplorerTabForCheckout: (params: ExplorerCheckoutContext & { tab: ExplorerTab }) => void;
   setExpandedPathsForWorkspace: (workspaceKey: string, paths: ExpandedPathsUpdate) => void;
-  setDiffExpandedPathsForWorkspace: (workspaceKey: string, paths: string[]) => void;
   setDiffCollapsedFoldersForWorkspace: (workspaceKey: string, dirPaths: string[]) => void;
   activateExplorerTabForCheckout: (checkout: ExplorerCheckoutContext) => void;
   setSidebarWidth: (width: number) => void;
@@ -148,7 +146,6 @@ export const usePanelStore = create<PanelState>()(
       explorerTab: "changes",
       explorerTabByCheckout: {},
       expandedPathsByWorkspace: {},
-      diffExpandedPathsByWorkspace: {},
       diffCollapsedFoldersByWorkspace: {},
       sidebarWidth: DEFAULT_SIDEBAR_WIDTH,
       explorerWidth: DEFAULT_EXPLORER_SIDEBAR_WIDTH,
@@ -276,13 +273,6 @@ export const usePanelStore = create<PanelState>()(
             },
           };
         }),
-      setDiffExpandedPathsForWorkspace: (workspaceKey, paths) =>
-        set((state) => ({
-          diffExpandedPathsByWorkspace: {
-            ...state.diffExpandedPathsByWorkspace,
-            [workspaceKey]: paths,
-          },
-        })),
       setDiffCollapsedFoldersForWorkspace: (workspaceKey, dirPaths) =>
         set((state) => ({
           diffCollapsedFoldersByWorkspace: {
@@ -308,7 +298,7 @@ export const usePanelStore = create<PanelState>()(
     }),
     {
       name: "panel-state",
-      version: 13,
+      version: 14,
       storage: createValidatedPersistStorage(AsyncStorage, PanelPersistedStateSchema),
       migrate: (persistedState, version) => migratePanelState(persistedState, version, { isWeb }),
       partialize: (state) => ({
@@ -316,7 +306,6 @@ export const usePanelStore = create<PanelState>()(
         explorerTab: state.explorerTab,
         explorerTabByCheckout: state.explorerTabByCheckout,
         expandedPathsByWorkspace: state.expandedPathsByWorkspace,
-        diffExpandedPathsByWorkspace: state.diffExpandedPathsByWorkspace,
         diffCollapsedFoldersByWorkspace: state.diffCollapsedFoldersByWorkspace,
         sidebarWidth: state.sidebarWidth,
         explorerWidth: state.explorerWidth,

packages/app/src/stores/panel-store/state.test.ts

@@ -120,6 +120,14 @@ describe("panel-store migration", () => {
     expect(state.diffCollapsedFoldersByWorkspace).toEqual({ ws: ["src/app"] });
   });
 
+  it("drops the retired per-file diff expansion state", () => {
+    const state = migratePanelState({ diffExpandedPathsByWorkspace: { ws: ["src/app.ts"] } }, 13, {
+      isWeb: false,
+    });
+
+    expect(state.diffExpandedPathsByWorkspace).toBeUndefined();
+  });
+
   it("replaces the dead explorer split ratio with the shared tree rail width", () => {
     const state = migratePanelState({ explorerFilesSplitRatio: 0.5 }, 12, { isWeb: false });
 

packages/app/src/stores/panel-store/state.ts

@@ -183,6 +183,7 @@ export const PanelPersistedStateSchema = z.strictObject({
   explorerTab: ExplorerTabSchema.optional(),
   explorerTabByCheckout: z.record(z.string(), ExplorerTabSchema).optional(),
   expandedPathsByWorkspace: z.record(z.string(), z.array(z.string())).optional(),
+  // Accepted only so migration can discard the former per-file diff expansion state.
   diffExpandedPathsByWorkspace: z.record(z.string(), z.array(z.string())).optional(),
   diffCollapsedFoldersByWorkspace: z.record(z.string(), z.array(z.string())).optional(),
   sidebarWidth: z.number().optional(),
@@ -290,13 +291,7 @@ export function migratePanelState(
   ) {
     state.expandedPathsByWorkspace = {};
   }
-  if (
-    version < 10 ||
-    typeof state.diffExpandedPathsByWorkspace !== "object" ||
-    !state.diffExpandedPathsByWorkspace
-  ) {
-    state.diffExpandedPathsByWorkspace = {};
-  }
+  delete state.diffExpandedPathsByWorkspace;
   if (
     version < 12 ||
     typeof state.diffCollapsedFoldersByWorkspace !== "object" ||

packages/app/src/stores/workspace-layout-store.test.ts

@@ -423,6 +423,25 @@ describe("workspace-layout-store actions", () => {
     expect(findPaneContainingTab(layout.root, "pull_request")?.id).toBe(explorerPaneId);
   });
 
+  it("places an auto-added pull request in the pane containing Changes", () => {
+    const workspaceKey = createWorkspaceKey();
+    const store = workspaceLayoutStore.getState();
+    store.openTabFocused(workspaceKey, { kind: "working_diff" });
+
+    useWorkspaceLayoutIds("explorer");
+    const explorerPaneId = store.splitPaneEmpty(workspaceKey, {
+      targetPaneId: "main",
+      position: "right",
+    });
+    store.setExplorerPaneId(workspaceKey, explorerPaneId);
+
+    store.observePullRequest(workspaceKey, "url:https://example.test/pulls/1");
+
+    const layout = workspaceLayoutStore.getState().layoutByWorkspace[workspaceKey];
+    expect(findPaneContainingTab(layout.root, "working_diff")?.id).toBe("main");
+    expect(findPaneContainingTab(layout.root, "pull_request")?.id).toBe("main");
+  });
+
   it("opens assistant files in an ensured explorer pane and reveals it on the next open", () => {
     const workspaceKey = createWorkspaceKey();
     const store = workspaceLayoutStore.getState();

packages/app/src/stores/workspace-layout-store.ts

@@ -521,10 +521,17 @@ export function createWorkspaceLayoutStore(
             }
 
             const layout = getWorkspaceLayout(state.layoutByWorkspace, normalizedWorkspaceKey);
+            const workingDiffTab = collectAllTabs(layout.root).find(
+              (tab) => tab.target.kind === "working_diff",
+            );
+            const workingDiffPane = workingDiffTab
+              ? findPaneContainingTab(layout.root, workingDiffTab.tabId)
+              : null;
             const explorerPaneId = state.explorerPaneIdByWorkspace[normalizedWorkspaceKey] ?? null;
             const explorerPane = findPaneById(layout.root, explorerPaneId);
-            const placementLayout = explorerPane
-              ? (focusPaneInLayout({ layout, paneId: explorerPane.id }) ?? layout)
+            const placementPane = workingDiffPane ?? explorerPane;
+            const placementLayout = placementPane
+              ? (focusPaneInLayout({ layout, paneId: placementPane.id }) ?? layout)
               : layout;
             const result = openTabInLayoutFocused({
               layout: placementLayout,