fix(writer): 防静默丢章告警 + 占位符正则宽容化（大小写/全角冒号）

src/genesis/qa/qa_loop.py

@@ -11,7 +11,7 @@ from genesis.qa.validator import QAValidator
 from genesis.writer.context_builder import build_contexts
 from genesis.writer.docx_injector import Block, DocxInjector
 from genesis.writer.models import ChapterContent
-from genesis.writer.orchestrator import _section_id_of
+from genesis.writer.orchestrator import _section_id_of, _warn_unanchored
 from genesis.writer.renderer import render_chapter_blocks
 from genesis.writer.writer_agent import WriterAgent
 from genesis.writer.writer_state import WriterState
@@ -23,6 +23,7 @@ class QALoop:
 
     def _build(self, structured_source, samples_dir, engine, prompt_registry, template_path, output_path, session_id, only_ids=None, prev=None):
         ctxs = build_contexts(structured_source, samples_dir)
+        _warn_unanchored(ctxs)
         state = WriterState([c.chapter_id for c in ctxs])
         agent = WriterAgent(session_id=session_id, engine=engine, prompt_registry=prompt_registry, state=state)
         contents_map = dict(prev) if prev else {}