refactor(video-pipeline): 移除 segments 机制，改为整段音频合成

移除 TTS 阶段逐句切分及 segments 数组逻辑，统一为整段音频合成。
CapCut 字幕切分由组装阶段按字符比例分配，简化音频上传、
时间线构建和字幕生成流程，减少冗余处理分支。

.claude/skills/video-from-script/scripts/capcut_assemble.js

@@ -65,24 +65,6 @@ async function batchUploadToOSS(inputDir, files, concurrency = 3) {
 async function batchUploadAudio(inputDir, items) {
   const urls = {}
   for (const item of items) {
-    if (item.segments && item.segments.length > 0) {
-      for (const seg of item.segments) {
-        if (!seg.audio || seg.audio.startsWith('http') || urls[seg.audio]) continue
-        const filePath = path.isAbsolute(seg.audio)
-          ? seg.audio
-          : path.resolve(inputDir, seg.audio)
-        if (!fs.existsSync(filePath)) {
-          console.error(`   音频文件不存在: ${filePath}`)
-          continue
-        }
-        try {
-          urls[seg.audio] = await uploadToOSS(filePath)
-          console.log(`   上传: ${path.basename(filePath)} -> OK`)
-        } catch (err) {
-          console.error(`   上传失败: ${path.basename(filePath)} - ${err.message}`)
-        }
-      }
-    }
     if (!item.audio || item.audio.startsWith('http')) {
       if (item.audio) urls[item.audio] = item.audio
       continue
@@ -174,17 +156,7 @@ async function assemble(args) {
   // ffprobe 测量实际时长
   let audioMeasured = 0, videoMeasured = 0
   for (const item of items) {
-    if (item.segments && item.segments.length > 0) {
-      for (const seg of item.segments) {
-        if (!seg.audio || seg.audio.startsWith('http')) continue
-        const audioPath = path.isAbsolute(seg.audio)
-          ? seg.audio
-          : path.resolve(inputDir, seg.audio)
-        if (!fs.existsSync(audioPath)) continue
-        const actualDur = await getAudioDurationSec(audioPath)
-        if (actualDur != null) { seg.duration = actualDur; audioMeasured++ }
-      }
-    } else if (item.audio && !item.audio.startsWith('http')) {
+    if (item.audio && !item.audio.startsWith('http')) {
       const audioPath = path.isAbsolute(item.audio)
         ? item.audio
         : path.resolve(inputDir, item.audio)
@@ -216,9 +188,7 @@ async function assemble(args) {
     const item = items[i]
     const tl = timeline[i]
     if (tl.skip) { console.log(`  [${i + 1}] 跳过（无音频）`); continue }
-    const audioDur = item.segments
-      ? item.segments.reduce((s, seg) => s + (seg.duration || 0), 0)
-      : (item.audioDuration || 0)
+    const audioDur = item.audioDuration || 0
     const slotDur = tl.duration / US
     const diff = slotDur - audioDur
     const videoDur = (item.videoDuration || 0)
@@ -341,14 +311,6 @@ async function assemble(args) {
             item.audio = audioUrls[item.audio]
             changed = true
           }
-          if (item.segments) {
-            for (const seg of item.segments) {
-              if (seg.audio && audioUrls[seg.audio]) {
-                seg.audio = audioUrls[seg.audio]
-                changed = true
-              }
-            }
-          }
         }
         if (changed) saveManifest(manifestFile, manifest)
       }