fix: 优化文章与页面表单的正文提交方式并改进必填项校验提示

src/lib/components/admin/MarkdownEditor.svelte

@@ -379,8 +379,6 @@
 		</button>
 	</div>
 
-	<!-- hidden textarea for form submission -->
-	<textarea name="content" style="display:none;" {value}></textarea>
 	<div bind:this={editorContainer} class="editor-container"></div>
 </div>
 

src/routes/admin/pages/[id]/+page.server.ts

@@ -43,8 +43,12 @@ export const actions: Actions = {
 		const slug = formData.get('slug')?.toString().trim();
 		const content = formData.get('content')?.toString() || '';
 
-		if (!title || !slug || !content) {
-			return fail(400, { error: '标题、URL 别名和正文为必填项' });
+		const missing: string[] = [];
+		if (!title) missing.push('标题');
+		if (!slug) missing.push('URL 别名');
+		if (!content) missing.push('正文');
+		if (missing.length > 0) {
+			return fail(400, { error: `${missing.join('、')}为必填项` });
 		}
 
 		try {

src/routes/admin/pages/[id]/+page.svelte

@@ -39,6 +39,8 @@
 {/if}
 
 <form action="?/update" method="POST" id="page-form" class="post-form">
+	<!-- 正文由页面统一持有并始终提交，避免切到「预览」时编辑器卸载导致正文丢失 -->
+	<input type="hidden" name="content" value={content} />
 	<div class="form-grid">
 		<div class="form-main">
 			<div class="form-group">

src/routes/admin/pages/new/+page.server.ts

@@ -17,8 +17,12 @@ export const actions: Actions = {
 		const slug = formData.get('slug')?.toString().trim();
 		const content = formData.get('content')?.toString() || '';
 
-		if (!title || !slug || !content) {
-			return fail(400, { error: '标题、URL 别名和正文为必填项' });
+		const missing: string[] = [];
+		if (!title) missing.push('标题');
+		if (!slug) missing.push('URL 别名');
+		if (!content) missing.push('正文');
+		if (missing.length > 0) {
+			return fail(400, { error: `${missing.join('、')}为必填项` });
 		}
 
 		try {

src/routes/admin/pages/new/+page.svelte

@@ -54,6 +54,8 @@
 {/if}
 
 <form method="POST" id="page-form" class="post-form">
+	<!-- 正文由页面统一持有并始终提交，避免切到「预览」时编辑器卸载导致正文丢失 -->
+	<input type="hidden" name="content" value={content} />
 	<div class="form-grid">
 		<div class="form-main">
 			<div class="form-group">

src/routes/admin/posts/[id]/+page.server.ts

@@ -87,8 +87,12 @@ export const actions: Actions = {
 		const publishedAt = formData.get('published_at')?.toString().trim();
 		const updatedAt = formData.get('updated_at')?.toString().trim() || new Date().toISOString();
 
-		if (!title || !slug || !content) {
-			return fail(400, { error: '标题、URL 别名和文章正文为必填项' });
+		const missing: string[] = [];
+		if (!title) missing.push('标题');
+		if (!slug) missing.push('URL 别名');
+		if (!content) missing.push('文章正文');
+		if (missing.length > 0) {
+			return fail(400, { error: `${missing.join('、')}为必填项` });
 		}
 
 		let seriesId: number | null;

src/routes/admin/posts/[id]/+page.svelte

@@ -122,6 +122,8 @@
 {/if}
 
 <form method="POST" action="?/update" id="post-form" class="post-form">
+	<!-- 正文由页面统一持有并始终提交，避免切到「预览」时编辑器卸载导致正文丢失 -->
+	<input type="hidden" name="content" value={content} />
 	<input type="hidden" name="published_at" value={publishedAt} />
 	<input type="hidden" name="updated_at" value={updatedAt} />
 	<div class="form-grid">

src/routes/admin/posts/new/+page.server.ts

@@ -52,8 +52,12 @@ export const actions: Actions = {
 		const publishedAt = formData.get('published_at')?.toString().trim() || new Date().toISOString();
 		const updatedAt = formData.get('updated_at')?.toString().trim() || publishedAt;
 
-		if (!title || !slug || !content) {
-			return fail(400, { error: '标题、URL 别名和文章正文为必填项' });
+		const missing: string[] = [];
+		if (!title) missing.push('标题');
+		if (!slug) missing.push('URL 别名');
+		if (!content) missing.push('文章正文');
+		if (missing.length > 0) {
+			return fail(400, { error: `${missing.join('、')}为必填项` });
 		}
 
 		let seriesId: number | null;

src/routes/admin/posts/new/+page.svelte

@@ -142,6 +142,8 @@
 {/if}
 
 <form method="POST" id="post-form" class="post-form">
+	<!-- 正文由页面统一持有并始终提交，避免切到「预览」时编辑器卸载导致正文丢失 -->
+	<input type="hidden" name="content" value={content} />
 	<input type="hidden" name="published_at" value={publishedAt} />
 	<input type="hidden" name="updated_at" value={updatedAt} />
 	<div class="form-grid">