fix: use filename fingerprint to prevent false positives on regular markdown

Check for .aider.chat.history.md specifically instead of matching any .md
file with #### headings. Addresses review feedback: CONTRIBUTING.md,
CHANGELOG.md, and API docs would have falsely triggered the Aider parser.

Add test_aider_rejects_generic_md to verify regular markdown files are not
parsed as Aider chat history.

Author: mvanhorn

mempalace/normalize.py

@@ -152,8 +152,8 @@ def normalize(filepath: str) -> str:
 
     ext = Path(filepath).suffix.lower()
 
-    # Try Aider markdown normalization
-    if ext == ".md" and sum(1 for line in lines if line.startswith("#### ")) >= 2:
+    # Try Aider markdown normalization (filename fingerprint to avoid false positives)
+    if ext == ".md" and Path(filepath).name == ".aider.chat.history.md":
         normalized = _try_aider_md(content)
         if normalized:
             return normalized

tests/test_normalize.py

@@ -83,7 +83,8 @@ def test_aider_md(tmp_path):
         "#### Can you also add tests for it?\n\n"
         "Sure, here's a test file.\n"
     )
-    f = tmp_path / "session.aider.chat.history.md"
+    # Must use Aider's exact filename to trigger the parser
+    f = tmp_path / ".aider.chat.history.md"
     f.write_text(content)
     result = normalize(str(f))
     assert "How do I add a new route?" in result