fix: keep RunSetup reachable with zero lanes, fix snapshot handling

Fixes regression from Tasks 1-2:
1. Run.defaultCwd.test.tsx was failing because LaneConsolePane wasn't
   rendering when no lane was selected (in layout-1 with zero lanes).
2. Added fallback rendering of LaneConsolePane in Workspace when
   !currentLane, so RunSetup stays reachable on fresh install.
3. Fixed early-return condition in LaneConsolePane to only show
   dropdown-only placeholder when showLaneSelector=true && laneId=null
   (split-view mode), not in layout-1 mode.
4. Added useEffect to sync cwd state with defaultCwd when it changes
   asynchronously from parent.
5. Updated LaneConsolePane tests to reflect correct behavior.
6. Regenerated snapshot to match layout-1 output.

client/src/components/run/LaneConsolePane.tsx

@@ -77,6 +77,12 @@ export function LaneConsolePane({
     onHasActiveRunChange?.(handle !== null);
   }, [handle, onHasActiveRunChange]);
 
+  useEffect(() => {
+    if (!currentLane && defaultCwd && cwd === "") {
+      setCwd(defaultCwd);
+    }
+  }, [defaultCwd, currentLane, cwd]);
+
   const refreshList = useCallback(() => {
     if (laneId !== null) {
       api.run
@@ -267,7 +273,7 @@ export function LaneConsolePane({
     setError(null);
   }, []);
 
-  if (laneId === null && !showLaneSelector) {
+  if (laneId === null && showLaneSelector) {
     return (
       <div data-testid="pane-empty" className="flex min-h-0 flex-1 flex-col gap-2 p-4">
         <select
@@ -354,9 +360,9 @@ export function LaneConsolePane({
         </div>
       )}
 
-      {!handle && laneId !== null ? (
+      {!handle ? (
         <RunSetup
-          laneId={laneId}
+          laneId={laneId ?? 0}
           prompt={prompt}
           onPromptChange={setPrompt}
           cwd={cwd}
@@ -378,8 +384,6 @@ export function LaneConsolePane({
           runHistory={runHistory}
           onResumeFromHistory={onResumeFromHistory}
         />
-      ) : !handle && laneId === null ? (
-        <p className="text-sm text-fg-muted">{tLanes("splitView.pickLane")}</p>
       ) : (
         <div className="flex-1 min-h-0 flex flex-col">
           <TerminalView