feat: Add diff issue creation after system prompt update

- Add step to get old SYSTEM_PROMPT value before updating
- Save old value to /tmp/old_value.txt using base64 encoding
- Add create-diff-issue job that runs after update:
  - Reads old value from temp file and new value from system_prompt.md
  - Generates diff showing changes between old and new values
  - Creates issue with title "[工作流] 提示词更新 <run_id>"
  - Issue body starts with "[工作流运行 #<run_id>](https://github.com/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID})"
  - Adds 'workflow' and 'documentation' labels to the issue

Co-Authored-By: Claude (mimo-v2-flash) <[email protected]>

Author: WhiteElephantIsNotARobot

.github/workflows/update-system-prompt.yml

@@ -20,6 +20,24 @@ jobs:
         with:
           fetch-depth: 1
 
+      - name: Get old SYSTEM_PROMPT value
+        id: get_old_value
+        run: |
+          echo "正在获取旧的 SYSTEM_PROMPT 值..."
+
+          # 获取旧值并保存到临时文件
+          OLD_VALUE=$(gh api /repos/${{ github.repository }}/actions/variables/SYSTEM_PROMPT --jq '.value' 2>/dev/null || echo "")
+
+          if [ -z "$OLD_VALUE" ]; then
+            echo "未找到现有的 SYSTEM_PROMPT 变量，将作为新变量创建"
+          else
+            echo "已获取旧值，长度: ${#OLD_VALUE} 字符"
+          fi
+
+          # 保存到临时文件（使用 base64 编码以避免特殊字符问题）
+          echo "$OLD_VALUE" | base64 -w 0 > /tmp/old_value.txt
+          echo "old_value_saved=true" >> $GITHUB_OUTPUT
+
       - name: Update SYSTEM_PROMPT variable
         run: |
           echo "正在更新 SYSTEM_PROMPT 变量..."
@@ -40,4 +58,64 @@ jobs:
             -f value="$SYSTEM_PROMPT_CONTENT"
 
           echo "✓ SYSTEM_PROMPT 变量已更新"
-          echo "文件大小: $(wc -c < system_prompt.md) 字符"
+          echo "文件大小: $(wc -c < system_prompt.md) 字符"
+
+      - name: Create diff issue
+        if: steps.get_old_value.outputs.old_value_saved == 'true'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            // 读取旧值
+            const fs = require('fs');
+            const oldValueBase64 = fs.readFileSync('/tmp/old_value.txt', 'utf8');
+            const oldValue = Buffer.from(oldValueBase64, 'base64').toString('utf-8');
+
+            // 读取新值
+            const newContent = fs.readFileSync('system_prompt.md', 'utf-8');
+
+            // 生成 diff
+            const diff = generateDiff(oldValue, newContent);
+
+            // 构建 issue 内容
+            const runUrl = `https://github.com/${process.env.GITHUB_REPOSITORY}/actions/runs/${process.env.GITHUB_RUN_ID}`;
+            const issueBody = `[工作流运行 #${process.env.GITHUB_RUN_ID}](${runUrl})\n\n${diff}`;
+
+            // 创建 issue
+            const issue = await github.rest.issues.create({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              title: `[工作流] 提示词更新 ${process.env.GITHUB_RUN_ID}`,
+              body: issueBody,
+              labels: ['workflow', 'documentation']
+            });
+
+            console.log(`✓ Issue created: #${issue.data.number}`);
+
+            function generateDiff(oldStr, newStr) {
+              const oldLines = oldStr.split('\n');
+              const newLines = newStr.split('\n');
+
+              let diff = '```diff\n';
+              diff += `--- 旧变量 (${oldLines.length} 行)\n`;
+              diff += `+++ 新变量 (${newLines.length} 行)\n`;
+
+              const maxLines = Math.max(oldLines.length, newLines.length);
+              for (let i = 0; i < maxLines; i++) {
+                const oldLine = oldLines[i];
+                const newLine = newLines[i];
+
+                if (oldLine === newLine) {
+                  diff += `  ${newLine}\n`;
+                } else if (oldLine && !newLine) {
+                  diff += `- ${oldLine}\n`;
+                } else if (!oldLine && newLine) {
+                  diff += `+ ${newLine}\n`;
+                } else {
+                  diff += `- ${oldLine}\n`;
+                  diff += `+ ${newLine}\n`;
+                }
+              }
+
+              diff += '```';
+              return diff;
+            }