fix(core): 交叉验证修复 — 单镜改稿按 DB 真实镜数(防截镜误扣)+ 模型框点外关闭选择器

critical:regenerate_segment_via_agent 改用 _draft_from_version 从 DB ScriptSegment 行重建基准稿(原读 stale content,用户增删镜后 normalize 会按 stale total_duration 截掉真实镜还照扣费)。低危:模型框容器补 chat-model-pick class,点外关闭选择器生效。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/backend/apps/ai/script_agent.py

@@ -675,6 +675,35 @@ def _load_base_draft(project, base_version_id: str) -> dict | None:
         return None
 
 
+def _draft_from_version(version) -> dict:
+    """从 ScriptVersion 的 DB 行(segments + metadata)重建 ScriptDraft —— 比解析可能已 stale 的 content 可靠
+    (用户增删/改镜后 content 不一定同步)。total_duration 按真实镜数算,避免 normalize 按 stale 值截/补镜。"""
+    meta = version.metadata or {}
+    segs = list(version.segments.order_by("sort_order"))
+    return {
+        "hook": meta.get("hook", ""),
+        "tone": meta.get("tone", ""),
+        "aspect_ratio": meta.get("aspect_ratio", "9:16"),
+        "total_duration": max(int(meta.get("total_duration") or 0), 15 * len(segs)) or 60,
+        "segment_count": len(segs),
+        "entities": meta.get("entities", []),
+        "segments": [
+            {
+                "index": s.sort_order,
+                "duration": s.duration_seconds or 15,
+                "role": s.role or "",
+                "narration": s.narration or "",
+                "speaker": s.speaker or None,
+                "visual": s.visual_prompt or "",
+                "product_exposure": s.product_exposure or "",
+                "entity_refs": s.entity_refs or [],
+                "dialogue": s.dialogue or [],
+            }
+            for s in segs
+        ],
+    }
+
+
 def regenerate_segment_via_agent(*, project, user, model_config: ModelConfig, segment, instruction: str = ""):
     """非流式·精准改一镜(「场次刷新」按钮复用 agent 单镜逻辑):读全脚本上下文,只重写该镜,落新 ScriptVersion。
     与 stream_script_agent 的 target_index 分支同源,但同步返回(不走 SSE)。计费 reserve→charge/release 闭环。"""
@@ -683,16 +712,13 @@ def regenerate_segment_via_agent(*, project, user, model_config: ModelConfig, se
     from apps.ai.services import build_provider, create_ai_task
     from apps.billing.services.ledger import charge_reserved_credit
 
-    base_version = segment.script_version
-    base_draft = _load_base_draft(project, str(base_version.id))
-    if base_draft is None:
-        raise ValueError("基准脚本无法解析,无法精准改镜")
+    base_draft = _draft_from_version(segment.script_version)  # 用 DB 行重建基准,别用可能 stale 的 content
     target_index = segment.sort_order
     aspect_ratio = (base_draft.get("aspect_ratio") or "9:16").strip()
-    total_duration = base_draft.get("total_duration") or 60
-    seg_n = len(base_draft.get("segments", []))
+    seg_n = len(base_draft.get("segments") or [])
     if not (0 <= target_index < seg_n):
         raise ValueError(f"镜号越界:第 {target_index + 1} 镜(共 {seg_n} 镜)")
+    total_duration = base_draft["total_duration"]  # 已按真实镜数算,normalize 不会截掉用户增删后的镜
 
     messages = build_agent_messages(
         project=project,