fix: decouple timeline from workspace layout

The regression recurred because a floating timeline height was still exported as shared layout space and its z-index exceeded artifacts and notices. Reserve zero layout height and define the timeline below artifact and notification overlays.

src/features/workbench/map-workbench-page.tsx

@@ -925,13 +925,7 @@ export function MapWorkbenchPage({
         {
           ...WORKBENCH_LAYOUT_CSS_VARIABLES,
           "--workbench-agent-current-width": `${currentAgentWidth}px`,
-          "--workbench-timeline-height": `${
-            !timelineVisible
-              ? 0
-              : !isLargeScreen
-                ? OPERATIONAL_TIMELINE_LAYOUT.mobileSummaryHeight + timelineBottom
-                : OPERATIONAL_TIMELINE_LAYOUT[timelineMode].height + timelineBottom
-          }px`
+          "--workbench-timeline-height": `${OPERATIONAL_TIMELINE_LAYOUT.overlayReservedHeight}px`
         } as CSSProperties
       }
     >
@@ -1094,7 +1088,7 @@ export function MapWorkbenchPage({
         {shouldShowTaskTicker ? (
           <motion.div
             key="agent-task-ticker-shell"
-            className="fixed left-1/2 right-auto top-24 z-20 w-[calc(100%-1.5rem)] [translate:-50%_0] md:absolute md:w-[var(--workbench-ticker-width)] 2xl:w-[var(--workbench-ticker-width-wide)]"
+            className="fixed left-1/2 right-auto top-24 z-50 w-[calc(100%-1.5rem)] [translate:-50%_0] md:absolute md:w-[var(--workbench-ticker-width)] 2xl:w-[var(--workbench-ticker-width-wide)]"
             style={{ transformOrigin: "top center" }}
             initial={
               prefersReducedMotion

src/features/workbench/operational-timeline/operational-timeline-model.test.ts

@@ -4,6 +4,7 @@ import {
   canCenterTimelineBesideMapScale,
   clusterOperationalEvents,
   createOperationalEvents,
+  OPERATIONAL_TIMELINE_LAYOUT,
   resolveTimelineScaleLayout
 } from "./operational-timeline-model";
 
@@ -15,6 +16,10 @@ const workOrder: ScheduledConditionItem = {
 };
 
 describe("operational timeline model", () => {
+  it("does not reserve workspace layout space for the floating timeline", () => {
+    expect(OPERATIONAL_TIMELINE_LAYOUT.overlayReservedHeight).toBe(0);
+  });
+
   it("creates linked plan and actual events for active work orders", () => {
     const events = createOperationalEvents([workOrder]);
     expect(events.map((event) => event.lane)).toEqual(["plan", "actual"]);

src/features/workbench/operational-timeline/operational-timeline-model.ts

@@ -38,7 +38,8 @@ export const OPERATIONAL_TIMELINE_LAYOUT = {
   mapScaleSafeWidth: 520,
   floatingGap: 48,
   edgeInset: 24,
-  scaleCollisionOffset: 56
+  scaleCollisionOffset: 56,
+  overlayReservedHeight: 0
 } as const;
 
 export type TimelineScaleLayout = {

src/features/workbench/workspace/artifact-peek-bar.tsx

@@ -17,7 +17,7 @@ export function ArtifactPeekBar({
     <aside
       aria-label="Agent 成果预览"
       className={cn(
-        "acrylic-panel pointer-events-auto absolute bottom-[calc(var(--workbench-timeline-height)+1rem)] z-30 flex min-h-[76px] w-[min(680px,calc(100%-2rem))] items-center gap-3 rounded-2xl border px-3 py-2.5 text-slate-900",
+        "acrylic-panel pointer-events-auto absolute top-28 z-40 flex min-h-[76px] w-[min(680px,calc(100%-2rem))] items-center gap-3 rounded-2xl border px-3 py-2.5 text-slate-900",
         "left-1/2 -translate-x-1/2",
         surfaceMode === "map_split" && "2xl:left-[25%]"
       )}

src/features/workbench/workspace/workbench-main-frame.tsx

@@ -95,7 +95,10 @@ export function WorkbenchMainFrame({
             id="artifact-workspace"
             aria-label={`${activeArtifact.title}工作区`}
             aria-hidden={!showArtifact}
-            className={cn("relative min-h-0 min-w-0 overflow-hidden", !showArtifact && "hidden")}
+            className={cn(
+              "relative z-30 min-h-0 min-w-0 overflow-hidden",
+              !showArtifact && "hidden"
+            )}
           >
             <AnalysisArtifactWorkspace
               artifact={activeArtifact}
@@ -119,7 +122,7 @@ export function WorkbenchMainFrame({
       </div>
 
       <motion.div
-        className="pointer-events-auto absolute left-3 z-40 mx-auto min-h-0"
+        className="pointer-events-auto absolute left-3 z-20 mx-auto min-h-0"
         initial={false}
         animate={{
           bottom: timelineBottom,