🤖 Cmd+2 returns focus to Review tab (#338)

## Summary

Pressing Cmd+2 (Ctrl+2 on Windows/Linux) while already on the Code
Review tab now returns keyboard focus to the panel, enabling immediate
keyboard navigation without clicking.

## Implementation

Uses a simple prop trigger pattern:
- `RightSidebar` increments `focusTrigger` counter when Cmd+2 is pressed
on active Review tab
- `ReviewPanel` watches trigger and calls `.focus()` on panel ref
- Hunk selection is preserved (doesn't jump to first hunk)

## Behavior

- **Cmd+1**: Switch to Costs tab
- **Cmd+2**: Switch to Review tab (or refocus if already active)
- **j/k/↑/↓**: Navigate between hunks (after panel has focus)
- **m**: Toggle hunk read/unread
- **Space**: Expand/collapse hunk

## Why This Matters

Code review with keyboard is faster when you can instantly return focus
from chat input to the review panel. Previously, you had to click on the
panel or tab through UI elements.

_Generated with `cmux`_

Author: ammar-agent

src/components/RightSidebar.tsx

@@ -179,6 +179,9 @@ const RightSidebarComponent: React.FC<RightSidebarProps> = ({
   // Global tab preference (not per-workspace)
   const [selectedTab, setSelectedTab] = usePersistedState<TabType>("right-sidebar-tab", "costs");
 
+  // Trigger for focusing Review panel (preserves hunk selection)
+  const [focusTrigger, setFocusTrigger] = React.useState(0);
+
   // Notify parent (AIView) of tab changes so it can enable/disable resize functionality
   React.useEffect(() => {
     onTabChange?.(selectedTab);
@@ -192,13 +195,18 @@ const RightSidebarComponent: React.FC<RightSidebarProps> = ({
         setSelectedTab("costs");
       } else if (matchesKeybind(e, KEYBINDS.REVIEW_TAB)) {
         e.preventDefault();
-        setSelectedTab("review");
+        // If already on Review tab, focus the panel
+        if (selectedTab === "review") {
+          setFocusTrigger((prev) => prev + 1);
+        } else {
+          setSelectedTab("review");
+        }
       }
     };
 
     window.addEventListener("keydown", handleKeyDown);
     return () => window.removeEventListener("keydown", handleKeyDown);
-  }, [setSelectedTab]);
+  }, [setSelectedTab, selectedTab]);
 
   const usage = useWorkspaceUsage(workspaceId);
   const [use1M] = use1MContext();
@@ -337,6 +345,7 @@ const RightSidebarComponent: React.FC<RightSidebarProps> = ({
                   workspaceId={workspaceId}
                   workspacePath={workspacePath}
                   onReviewNote={onReviewNote}
+                  focusTrigger={focusTrigger}
                 />
               </div>
             )}

src/components/RightSidebar/CodeReview/ReviewPanel.tsx

@@ -25,6 +25,8 @@ interface ReviewPanelProps {
   workspaceId: string;
   workspacePath: string;
   onReviewNote?: (note: string) => void;
+  /** Trigger to focus panel (increment to trigger) */
+  focusTrigger?: number;
 }
 
 const PanelContainer = styled.div`
@@ -274,7 +276,9 @@ export const ReviewPanel: React.FC<ReviewPanelProps> = ({
   workspaceId,
   workspacePath,
   onReviewNote,
+  focusTrigger,
 }) => {
+  const panelRef = useRef<HTMLDivElement>(null);
   const [hunks, setHunks] = useState<DiffHunk[]>([]);
   const [selectedHunkId, setSelectedHunkId] = useState<string | null>(null);
   const [isLoadingHunks, setIsLoadingHunks] = useState(true);
@@ -322,6 +326,13 @@ export const ReviewPanel: React.FC<ReviewPanelProps> = ({
     includeUncommitted: includeUncommitted,
   });
 
+  // Focus panel when focusTrigger changes (preserves current hunk selection)
+  useEffect(() => {
+    if (focusTrigger && focusTrigger > 0) {
+      panelRef.current?.focus();
+    }
+  }, [focusTrigger]);
+
   // Load file tree - when workspace, diffBase, or refreshTrigger changes
   useEffect(() => {
     let cancelled = false;
@@ -633,6 +644,7 @@ export const ReviewPanel: React.FC<ReviewPanelProps> = ({
 
   return (
     <PanelContainer
+      ref={panelRef}
       tabIndex={0}
       onFocus={() => setIsPanelFocused(true)}
       onBlur={() => setIsPanelFocused(false)}