Synchronize chapter and navigation translations with Chinese prose indentation

src/translation/llm_client.py

@@ -144,6 +144,7 @@ Output Format:
         """
         id_map = {}  # short_id -> entry_id
         lines = []
+        title_notes = []
         
         for i, item in enumerate(items, 1):
             short_id = f"#{i}"
@@ -151,9 +152,18 @@ Output Format:
             
             # Clean text (remove extra whitespace)
             text = re.sub(r'\s+', ' ', item.original_text).strip()
+            if item.context and item.context.startswith('navigation-'):
+                title_notes.append(f"{short_id}: {item.context}")
             lines.append(f"{short_id}: {text}")
         
-        return id_map, "\n".join(lines)
+        if title_notes:
+            instructions = ("Title context (instructions only; do not copy into translations):\n"
+                            "Translate Chapter N as 第N章, Part N as 第N部, and translate the title itself. "
+                            "Keep number/subtitle styling tokens in their original regions.\n"
+                            + "\n".join(title_notes) + "\n\nSource units:\n")
+        else:
+            instructions = ""
+        return id_map, instructions + "\n".join(lines)
 
     def _parse_short_id_response(self, response: str, id_map: Dict[str, str]) -> Dict[str, str]:
         """