feat: 封面生成流水线、执黑先行二号风格扩展、账号配置更新

- 新增 gen-covers 系列脚本（kling/gpt/t2i/batch/direct/final等方案）
- 执黑先行二号添加9种风格提示词目录（梦核/剪纸/水墨/毛毡/硬核线条等）
- 执黑先行添加封面提示词、执黑先行二号更新图片提示词
- product_viral_factory 账号配置扩充并添加 cover_template 参考图
- capcut_assemble/kling-video-generator/oss-upload/poll-utils 细节修复
- CLAUDE.md 更新流程文档

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/skills/video-from-script/scripts/lib/video-poll-utils.js

@@ -12,7 +12,8 @@ const fs = require('fs')
 const https = require('https')
 const http = require('http')
 
-const TRANSIENT_RE = /timeout|ECONNRESET|ETIMEDOUT|network|socket|超时|processing|pending/i
+// "fetch failed" = Node fetch threw before receiving a response (network error, NOT a Kling task failure)
+const TRANSIENT_RE = /timeout|ECONNRESET|ETIMEDOUT|network|socket|超时|processing|pending|fetch failed/i
 
 const TASK_FAILED_RE = /\bfailed\b|失败/i
 
@@ -104,8 +105,11 @@ function makePollWithRetry({ Api, suffix, duration, maxRetries = 3, optimizeProm
           }
         } catch (err) {
           lastError = err.message
-          lastErrorWasTaskFailure = isTaskFailed(err)
-          if (isTransientError(err) && pollAttempt < POLL_RETRIES) {
+          // Network errors (transient) must never be treated as task failures.
+          // isTaskFailed("fetch failed") would be true without this guard because "failed" matches TASK_FAILED_RE.
+          const transient = isTransientError(err)
+          lastErrorWasTaskFailure = !transient && isTaskFailed(err)
+          if (transient && pollAttempt < POLL_RETRIES) {
             const tag = isTaskFailed(err) ? '失败' : '超时/瞬断'
             console.log(`   ⚠ 轮询${tag} (${pollAttempt + 1}/${POLL_RETRIES}): ${err.message.slice(0, 60)}`)
             await new Promise(r => setTimeout(r, POLL_RETRY_DELAY))