fix(ui): refine acrylic controls and timeline interactions

Restore full acrylic materials to stacked task cards and floating controls.
Extend the map behind the navigation header while preserving document and
control insets. Align timeline and scale readouts, refresh dense-marker
hover content, and highlight model and approval menu options.

Keep narrow timeline headers clear of their legend and actions. Update
coupled geometry checks and retain city zoom-12 and menu regression coverage.

Validation: scoped git diff --check and read-only UI geometry inspection.
Test suites were not rerun at the user's request.

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

@@ -72,9 +72,10 @@ export function WorkbenchMainFrame({
     ? { duration: 0 }
     : { duration: 0.24, ease: [0.22, 1, 0.36, 1] as const };
 
+  // Map imagery fills the header backdrop; documents and controls reserve the header inset.
   return (
     <div
-      className="workbench-main-frame pointer-events-none absolute inset-x-0 bottom-0 top-14 min-h-0 lg:left-[var(--workbench-agent-current-width)]"
+      className="workbench-main-frame pointer-events-none absolute inset-0 min-h-0 lg:left-[var(--workbench-agent-current-width)]"
       data-testid="workbench-main-frame"
       data-timeline-mode={timelineMode}
     >
@@ -108,7 +109,7 @@ export function WorkbenchMainFrame({
               aria-label={`${activeArtifact.title}工作区`}
               aria-hidden={!showArtifact}
               className={cn(
-                "z-30 min-h-0 min-w-0 overflow-hidden",
+                "z-30 mt-14 min-h-0 min-w-0 overflow-hidden",
                 surfaceMode === "focus" && "lg:pl-[84px]",
                 showArtifact ? "relative" : "pointer-events-none absolute inset-0"
               )}