fix(memory): resolve() the shared-connection registry key; symlink test

Follow-ups for salvaged PR #43819: the registry key was
str(Path(db_path).expanduser()) — a symlinked or relative path to the
same DB file got its own connection, silently reintroducing the exact
multi-writer contention the registry prevents. Key on Path.resolve()
(OSError-tolerant fallback). Adds a symlink regression test and the
AUTHOR_MAP entry for adambiggs.

tests/plugins/memory/test_holographic_store.py

@@ -68,6 +68,24 @@ class TestSharedConnection:
             a.close()
             b.close()
 
+    def test_symlinked_path_shares_connection(self, tmp_path):
+        """A symlink to the same DB file must hit the same registry entry —
+        otherwise two connections to one file silently reintroduce the
+        multi-writer contention the registry exists to prevent."""
+        real_dir = tmp_path / "real"
+        real_dir.mkdir()
+        link_dir = tmp_path / "link"
+        link_dir.symlink_to(real_dir)
+
+        a = MemoryStore(real_dir / "memory_store.db")
+        b = MemoryStore(link_dir / "memory_store.db")
+        try:
+            assert a._conn is b._conn
+            assert len(MemoryStore._shared) == 1
+        finally:
+            a.close()
+            b.close()
+
     def test_writes_visible_across_instances(self, db_path):
         a = MemoryStore(db_path)
         b = MemoryStore(db_path)