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/pages/canvas/shared.tsx

@@ -223,7 +223,7 @@ export default function SharedCanvasPage() {
 
     return (
         <main className="relative h-screen overflow-hidden" style={{ background: theme.canvas.background, color: theme.node.text }}>
-            <header className="pointer-events-none absolute inset-x-0 top-0 z-[80] flex h-16 items-center justify-between px-5">
+            <header className="pointer-events-none absolute inset-x-0 top-0 z-[var(--z-panel-floating)] flex h-16 items-center justify-between px-5">
                 <div className="pointer-events-auto flex min-w-0 items-center gap-3">
                     <Share2 className="size-4" style={{ color: theme.node.muted }} />
                     <span className="max-w-[45vw] truncate text-base font-semibold">{title}</span>
@@ -258,8 +258,8 @@ export default function SharedCanvasPage() {
 
             <CanvasNodeHoverToolbar node={dragRef.current ? null : toolbarNode} viewport={viewport} containerRef={containerRef} onKeep={keepToolbar} onLeave={hideToolbar} onInfo={(node) => setInfoNodeId(node.id)} onEditText={unauthorized} onDecreaseFont={unauthorized} onIncreaseFont={unauthorized} onToggleDialog={unauthorized} onAnnotate={unauthorized} onGenerateImage={unauthorized} onUpload={unauthorized} onDownload={unauthorized} onSaveAsset={unauthorized} onMaskEdit={unauthorized} onEmotion={unauthorized} onPortraitTexture={unauthorized} onCrop={unauthorized} onSplit={unauthorized} onUpscale={unauthorized} onSuperResolve={unauthorized} onAngle={unauthorized} onViewImage={unauthorized} onExtractVideoLastFrame={unauthorized} extractingVideoFrame={false} onReversePrompt={unauthorized} onRetry={unauthorized} onToggleFreeResize={unauthorized} onToggleLocked={unauthorized} onDelete={unauthorized} />
 
-            <div className="absolute bottom-5 left-5 z-[70]"><CanvasZoomControls scale={viewport.k} containerRef={containerRef} onScaleChange={setZoom} onReset={resetViewport} isMiniMapOpen={false} onToggleMiniMap={unauthorized} onOpenShortcuts={unauthorized} /></div>
-            <div className="pointer-events-none absolute bottom-5 right-5 z-[70] max-w-[340px] text-right text-xs leading-5" style={{ color: theme.node.muted }}>访客操作仅在当前页面临时生效</div>
+            <div className="absolute bottom-5 left-5 z-[var(--z-panel-floating)]"><CanvasZoomControls scale={viewport.k} containerRef={containerRef} onScaleChange={setZoom} onReset={resetViewport} isMiniMapOpen={false} onToggleMiniMap={unauthorized} onOpenShortcuts={unauthorized} /></div>
+            <div className="pointer-events-none absolute bottom-5 right-5 z-[var(--z-panel-floating)] max-w-[340px] text-right text-xs leading-5" style={{ color: theme.node.muted }}>访客操作仅在当前页面临时生效</div>
 
             {contextMenu ? <SharedContextMenu menu={contextMenu} onAdd={addNode} onInfo={() => { if (contextMenu.nodeId) setInfoNodeId(contextMenu.nodeId); setContextMenu(null); }} onUnauthorized={() => { setContextMenu(null); unauthorized(); }} /> : null}
             <CanvasNodeInfoModal node={infoNode} open={Boolean(infoNode)} onClose={() => setInfoNodeId(null)} readOnly onUnauthorized={unauthorized} />
@@ -269,7 +269,7 @@ export default function SharedCanvasPage() {
 
 function SharedContextMenu({ menu, onAdd, onInfo, onUnauthorized }: { menu: ContextMenu; onAdd: (type: CanvasNodeType) => void; onInfo: () => void; onUnauthorized: () => void }) {
     const theme = canvasThemes[useThemeStore((state) => state.theme)];
-    return <div data-canvas-no-zoom className="absolute z-[90] min-w-48 rounded-lg border p-1.5 shadow-xl" style={{ left: menu.x, top: menu.y, background: theme.toolbar.panel, borderColor: theme.toolbar.border, color: theme.node.text }} onMouseDown={(event) => event.stopPropagation()}>
+    return <div data-canvas-no-zoom className="absolute z-[var(--z-modal)] min-w-48 rounded-lg border p-1.5 shadow-xl" style={{ left: menu.x, top: menu.y, background: theme.toolbar.panel, borderColor: theme.toolbar.border, color: theme.node.text }} onMouseDown={(event) => event.stopPropagation()}>
         {menu.nodeId ? <><MenuButton icon={<Eye />} label="查看节点信息" onClick={onInfo} /><MenuButton icon={<LockKeyhole />} label="编辑或生成" onClick={onUnauthorized} /></> : <>
             <div className="px-2 py-1.5 text-[var(--fs-label)]" style={{ color: theme.node.muted }}>添加临时节点</div>
             <MenuButton icon={<FileText />} label="文本节点" onClick={() => onAdd(CanvasNodeType.Text)} />