refactor(canvas): 浮层体系重构 — z-index 14档+专注模式+工具栏click触发 #126 #127 #128 (#129)

按视觉层重设计 z-index（12→14 档），新增节点层/激活节点层/节点工具栏层等
语义 token，并下沉节点内部 stacking context（--node-z-content/overlay/handle）
与 dock 子面板（--dock-z-popover），消除硬编码 z 值。

新增专注模式（避让分屏可切换）：use-focus-mode 管理 localStorage 偏好与小屏
（<1024px）强制避让；助手面板从 flex 改为 absolute + 垂直分槽（顶部 288px
让位活动任务面板），画布区按面板宽度动态 padding；顶栏新增 PanelRight
切换按钮并带强制态反馈。

节点工具栏由 hover+select 触发放为 click-only（选中即显），组件由
canvas-node-hover-toolbar 重命名为 canvas-node-toolbar；移除 project 与
render-model 中冗余的 toolbarNodeId 状态。

活动任务面板 z-index 由 --z-modal-overlay(110) 降至 --z-panel-floating(80)，
归位浮动面板层；AGENTS.md Elevation 同步至 14 档。

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

web/src/components/canvas/canvas-toolbar.tsx

@@ -175,7 +175,7 @@ export function CanvasToolbar({
     const resourceCommands = addNodeCommands.filter((cmd) => cmd.section === "resource").map(toCommand);
 
     return (
-        <div ref={rootRef} data-canvas-no-zoom className="pointer-events-none absolute inset-x-4 bottom-4 z-50 flex justify-center">
+        <div ref={rootRef} data-canvas-no-zoom className="pointer-events-none absolute inset-x-4 bottom-4 z-[var(--z-toolbar)] flex justify-center">
             <AnimatePresence>
                 {addOpen ? (
                     <AddNodeMenu
@@ -191,7 +191,7 @@ export function CanvasToolbar({
 
             <AnimatePresence>
                 {appearanceOpen ? (
-                    <motion.div initial={{ opacity: 0 }} animate={{ opacity: 1 }} exit={{ opacity: 0 }} transition={{ duration: aceternityMotion.duration.instant }} className="pointer-events-auto absolute bottom-[50px] z-30 w-[224px] max-w-[calc(100vw-24px)] -translate-x-1/2" style={{ left: panelX || "50%" }}>
+                    <motion.div initial={{ opacity: 0 }} animate={{ opacity: 1 }} exit={{ opacity: 0 }} transition={{ duration: aceternityMotion.duration.instant }} className="pointer-events-auto absolute bottom-[50px] z-[var(--dock-z-popover)] w-[224px] max-w-[calc(100vw-24px)] -translate-x-1/2" style={{ left: panelX || "50%" }}>
                         <SpotlightSurface spotlightColor={theme.toolbar.itemHover} initial={{ y: 6, scale: 0.97 }} animate={{ y: 0, scale: 1 }} exit={{ y: 4, scale: 0.98 }} transition={{ duration: aceternityMotion.duration.instant, ease: aceternityMotion.easing.enter }} className="aceternity-floating-panel overflow-hidden rounded-[var(--panel-radius)] border p-2.5 backdrop-blur-2xl" style={{ background: theme.spatial.elevated, borderColor: theme.toolbar.border, color: theme.toolbar.item, boxShadow: `0 24px 64px ${theme.spatial.shadow}` }} onWheel={(event) => event.stopPropagation()}>
                             <PanelHeading icon={<Palette className="size-4" />} title="画布外观" subtitle="调整整个创作空间" theme={theme} />
                             <div className="mt-3 text-[var(--fs-micro)] font-semibold uppercase opacity-45">主题模式</div>
@@ -231,7 +231,7 @@ function AddNodeMenu({ x, theme, nodeCommands, resourceCommands }: {
     resourceCommands: CanvasCreateCommand[];
 }) {
     return (
-        <motion.div initial={{ opacity: 0 }} animate={{ opacity: 1 }} exit={{ opacity: 0 }} transition={{ duration: aceternityMotion.duration.instant }} className="pointer-events-auto absolute bottom-[50px] z-40 w-[260px] max-w-[calc(100vw-24px)] -translate-x-1/2" style={{ left: x || "50%" }}>
+        <motion.div initial={{ opacity: 0 }} animate={{ opacity: 1 }} exit={{ opacity: 0 }} transition={{ duration: aceternityMotion.duration.instant }} className="pointer-events-auto absolute bottom-[50px] z-[var(--dock-z-popover)] w-[260px] max-w-[calc(100vw-24px)] -translate-x-1/2" style={{ left: x || "50%" }}>
             <SpotlightSurface spotlightColor={theme.toolbar.itemHover} initial={{ y: 6, scale: 0.97 }} animate={{ y: 0, scale: 1 }} exit={{ y: 4, scale: 0.98 }} transition={{ duration: aceternityMotion.duration.instant, ease: aceternityMotion.easing.enter }} className="aceternity-floating-panel overflow-hidden rounded-[var(--panel-radius)] border p-2 backdrop-blur-2xl" style={{ background: theme.spatial.elevated, borderColor: theme.toolbar.border, color: theme.node.text, boxShadow: `0 24px 64px ${theme.spatial.shadow}` }} onWheel={(event) => event.stopPropagation()}>
                 <PanelHeading icon={<Plus className="size-4" />} title="创建内容" subtitle="选择节点类型" theme={theme} />
                 <MenuSection title="创作节点" />