fix(canvas): 主题存储 - 修复非法 theme 值导致 /create 崩溃 (#155)

useThemeStore persist 无 merge 校验,坏 session/后端同步失败时可能将
非法 theme 值写入 localStorage,导致 canvasThemes[非法值] 为 undefined,
渲染时访问 theme.node 抛出 "Cannot read properties of undefined
(reading 'node')",/create 页面崩溃。

4 层防线(只加校验,不回退代码):
- useThemeStore persist merge 白名单校验,非法值回退 dark
- useThemeStore setTheme 写入前校验,防止同步路径绕过 merge
- normalizeConfigSnapshot 入口兜底 undefined/partial 快照
- ModelPicker 与 CanvasResourceMentionTextarea 消费端加 fallback

Closes #154

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

web/src/components/canvas/canvas-resource-mention-textarea.tsx

@@ -45,7 +45,8 @@ export const CanvasResourceMentionTextarea = forwardRef<HTMLTextAreaElement, Pro
     { value, references, onChange, onSubmit, onKeyDown, className, containerClassName, style, highlightLabels = true, mentionMenuWidth = 256, sendOnEnter = true, onContentSizeChange, ...props },
     forwardedRef,
 ) {
-    const theme = canvasThemes[useThemeStore((state) => state.theme)];
+    const rawTheme = useThemeStore((state) => state.theme);
+    const theme = canvasThemes[rawTheme as keyof typeof canvasThemes] ?? canvasThemes.dark;
     const containerRef = useRef<HTMLDivElement | null>(null);
     const textareaRef = useRef<HTMLTextAreaElement | null>(null);
     const editorRef = useRef<HTMLDivElement | null>(null);

web/src/components/model-picker.tsx

@@ -2,7 +2,7 @@ import { useEffect, useId, useMemo, useRef, useState, type KeyboardEvent } from
 import { Check, ChevronDown, Coins, Cpu } from "lucide-react";
 import { Popover } from "antd";
 
-import { canvasThemes } from "@/lib/canvas-theme";
+import { canvasThemes, type CanvasTheme } from "@/lib/canvas-theme";
 import { cn } from "@/lib/utils";
 import { modelDisplayName, modelOptionLabel, modelOptionName, resolveModelChannel, selectableModelsByCapability, type AiConfig, type ModelCapability } from "@/stores/use-config-store";
 import { useThemeStore } from "@/stores/use-theme-store";
@@ -24,7 +24,9 @@ type ModelPickerProps = {
 export function ModelPicker({ config, value, onChange, capability, className, fullWidth = false, placeholder = "选择模型", onMissingConfig, showSelectedPrice = true, variant = "default" }: ModelPickerProps) {
     const creditsEnabled = useUserStore((state) => state.features.creditsEnabled);
     const pickerId = useId();
-    const theme = canvasThemes[useThemeStore((state) => state.theme)];
+    // 双保险：即使 store merge 写出非法 theme，这里也兜底到 dark，避免 "reading 'node'" 崩溃
+    const rawTheme = useThemeStore((state) => state.theme);
+    const theme = (canvasThemes[rawTheme as keyof typeof canvasThemes] ?? canvasThemes.dark) as CanvasTheme;
     const [open, setOpen] = useState(false);
     const menuRef = useRef<HTMLDivElement>(null);
     const triggerRef = useRef<HTMLButtonElement>(null);