feat(canvas): 面板层级管理 — 五层Elevation体系+渐进式三区+z-index全量迁移 #98 (#102)

* feat(canvas): 面板层级管理优化 - 五层Elevation+渐进式三区+进度增强 #98 #94

基于 Wayfinder 地图 #98 决议执行面板层级管理优化：

1. 五层 Elevation 体系（决策1）
   - 画布组件 z-index 硬编码值全部迁移到 token
   - L0 画布层 → L1 工具层 → L2 面板层 → L3 对话框层 → L4 通知层
   - 涉及 14 个 .tsx 文件，0 处 z-[N] 硬编码残留

2. prompt 面板渐进式三区（决策2）
   - B区参数区改为手风琴折叠模式（默认折叠）
   - 新增 SlidersHorizontal + ChevronDown 图标切换
   - 点击展开 video 工具参数，收起后释放视觉空间
   - A区核心区（prompt+生成）始终展开

3. 任务进度条增强（决策3）
   - 进度条高度 1px→1.5px，视觉更醒目
   - 新增 shimmer 扫描动画（running 态，1.4s/cycle）
   - 新增百分比数字显示（tabular-nums 等宽数字）
   - 新增 indeterminate 模式（无百分比时循环扫描）
   - 尊重 prefers-reduced-motion（reducedMotion 时禁用动画）

4. CSS 动画
   - 新增 @keyframes canvas-task-progress-shimmer
   - .canvas-task-progress-shimmer 类

Closes #98

* refactor(canvas): z-index 全量迁移到五层Elevation token #98 #94

补全 #98 五层 Elevation 体系的剩余硬编码 z-index 清理：
- 三个设置弹层（图/音/视频）zIndex:1200 → var(--z-popover)
- model-setup-guide z-[900] → var(--z-toast)
- 项目侧栏 z-30 → var(--z-panel)，章节预览 z-50 → var(--z-panel-floating)
- shared 页头/缩放控件/访客提示 z-[80]/z-[70] → var(--z-panel-floating)，右键菜单 z-[90] → var(--z-modal)
- project 缩放控件容器 z-50 → var(--z-panel)，绘图加载遮罩 z-[500] → var(--z-toast)
- 反馈面板 z-[90] → var(--z-panel-floating)

共 16 处全局浮层 z-index 迁移到 token，消除层级冲突隐患。

---------

Co-authored-by: sikongyue <3155157671@qq.com>

web/src/components/canvas/canvas-emotion-workspace.tsx

@@ -207,7 +207,7 @@ function FaceSelectionOverlay({ node, viewport, containerRef, imageWidth, imageH
         <div
             ref={overlayRef}
             data-canvas-no-zoom
-            className={`absolute z-[105] overflow-hidden rounded-[var(--r-2xl)] ${status === "manual" ? "cursor-crosshair touch-none" : "pointer-events-none"}`}
+            className={`absolute z-[var(--z-modal)] overflow-hidden rounded-[var(--r-2xl)] ${status === "manual" ? "cursor-crosshair touch-none" : "pointer-events-none"}`}
             style={{ left: 0, top: 0, width: node.width * viewport.k, height: node.height * viewport.k }}
             onPointerDown={status === "manual" ? (event) => {
                 event.preventDefault();
@@ -287,7 +287,7 @@ function SelectionToolbar({ node, viewport, containerRef, status, faceCount, err
             initial={reducedMotion ? { opacity: 0 } : { opacity: 0, y: -5, scale: 0.96 }}
             animate={{ opacity: 1, y: 0, scale: 1 }}
             transition={reducedMotion ? { duration: 0 } : aceternityMotion.spring.panel}
-            className="aceternity-floating-panel absolute z-[125] flex h-12 w-[420px] max-w-[calc(100%_-_24px)] items-center rounded-[15px] border px-2 backdrop-blur-2xl"
+            className="aceternity-floating-panel absolute z-[var(--z-modal-overlay)] flex h-12 w-[420px] max-w-[calc(100%_-_24px)] items-center rounded-[15px] border px-2 backdrop-blur-2xl"
             style={{ left: 12, top: 76, background: theme.spatial.elevated, borderColor: theme.toolbar.border, color: theme.node.text, boxShadow: `0 22px 60px ${theme.spatial.shadow}` }}
             onPointerDown={(event) => event.stopPropagation()}
         >
@@ -305,7 +305,7 @@ function SelectionToolbar({ node, viewport, containerRef, status, faceCount, err
 function EmotionPanelOverlay({ node, viewport, containerRef, children }: { node: CanvasNodeData; viewport: ViewportTransform; containerRef: RefObject<HTMLDivElement | null>; children: ReactNode }) {
     const panelRef = useRef<HTMLDivElement>(null);
     useScreenAnchor(panelRef, node, viewport, containerRef, (next, container) => panelScreenRect(node, next, container, panelRef.current));
-    return <div ref={panelRef} data-canvas-no-zoom className="absolute z-[120] w-[580px] max-w-[calc(100%_-_24px)]" style={{ left: 12, top: 76 }} onPointerDown={(event) => event.stopPropagation()}>{children}</div>;
+    return <div ref={panelRef} data-canvas-no-zoom className="absolute z-[var(--z-modal-overlay)] w-[580px] max-w-[calc(100%_-_24px)]" style={{ left: 12, top: 76 }} onPointerDown={(event) => event.stopPropagation()}>{children}</div>;
 }
 
 function useScreenAnchor(ref: RefObject<HTMLElement | null>, node: CanvasNodeData, viewport: ViewportTransform, containerRef: RefObject<HTMLDivElement | null>, resolve: (viewport: ViewportTransform, container: HTMLDivElement) => { left: number; top: number; width?: number; height?: number }) {