fix(compiler): add [[entities/X]] whitelist rule + restore concept-topic guard

Remaining review findings after a7a06ed:
- _KNOWN_TARGETS_USER now states the [[entities/Z]] rule, so entity links
  the LLM is told to write aren't silently stripped as ghosts.
- Restore the dropped 'Do NOT create concepts that are just the document
  topic itself' plan rule to prevent redundant title-mirror concepts.

Author: KylinMountain

openkb/agent/compiler.py

@@ -113,6 +113,7 @@
   sparse documents.
 - Prefer "update" over "create" for any concept or entity already listed above.
 - Do NOT create a concept/entity that overlaps an existing one — use "update".
+- Do NOT create concepts that are just the document topic itself.
 - "related" is lightweight cross-linking only, no content rewrite.
 
 Return ONLY valid JSON, no fences, no explanation.
@@ -127,8 +128,9 @@
 Rules for [[wikilinks]] in all subsequent responses:
 - For [[concepts/X]]: X must appear in the whitelist above.
 - For [[summaries/Y]]: Y must appear in the whitelist above.
+- For [[entities/Z]]: Z must appear in the whitelist above.
 - Do NOT invent new wikilink targets. If you want to mention a concept \
-that is not in the whitelist, write it as plain text without brackets.
+or entity that is not in the whitelist, write it as plain text without brackets.
 """
 
 _CONCEPT_PAGE_USER = """\

tests/test_compiler.py

@@ -1672,3 +1672,21 @@ def test_schema_declares_entities():
     assert "Entity Page" in AGENTS_MD
     for t in ("person", "organization", "place", "product", "work", "event", "other"):
         assert t in AGENTS_MD
+
+
+def test_known_targets_prompt_has_entities_rule():
+    """The whitelist message must tell the LLM the [[entities/X]] rule, since
+    entity-page prompts instruct writing such links; otherwise entity links
+    are generated freely and then stripped as ghosts."""
+    from openkb.agent.compiler import _KNOWN_TARGETS_USER
+
+    assert "[[entities/" in _KNOWN_TARGETS_USER
+
+
+def test_plan_prompt_keeps_topic_itself_guard():
+    """The concept-plan prompt must retain the guard against creating a concept
+    that merely mirrors the document's own topic."""
+    from openkb.agent.compiler import _CONCEPTS_PLAN_USER
+
+    assert "just the document topic itself" in _CONCEPTS_PLAN_USER
+