fix(core): strip null bytes from markdown content before database insert

PostgreSQL rejects null bytes (0x00) in text columns, causing
CharacterNotInRepertoireError when syncing files like Claude agent
definitions that contain embedded nulls. SQLite silently accepts them,
so this only surfaces in cloud environments.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: phernandez <paul@basicmachines.co>

src/basic_memory/markdown/entity_parser.py

@@ -249,6 +249,10 @@ class EntityParser:
 
         content = strip_bom(content)
 
+        # PostgreSQL rejects null bytes (0x00) in text columns.
+        # Some markdown files (e.g. Claude agent definitions) contain embedded nulls.
+        content = content.replace("\x00", "")
+
         # Parse frontmatter with proper error handling for malformed YAML.
         # We use frontmatter.parse() instead of frontmatter.loads() because
         # loads() does Post(content, handler, **metadata), which crashes when