Re-implement needed features without debug cruft

- Add Features section to README documenting key capabilities
- Add mode=light parameter to embed examples
- Enhance environment variable handling with ${VAR:-default} syntax
- Fix Python 3 compatibility in short_id_to_bytes()
- Fix email verification logic with proper null check
- Add session size limits for pending nodes
- Add CLAUDE.md configuration for commit attribution

CLAUDE.md

@@ -0,0 +1,16 @@
+# Claude Code Configuration
+
+## Commit Attribution
+
+When creating git commits, use clean, simple commit messages:
+
+```
+Commit message here.
+```
+
+**Do NOT include:**
+- `🤖 Generated with [Claude Code](https://claude.com/claude-code)`
+- `Co-Authored-By: Claude <noreply@anthropic.com>`
+- Any fake corporate entities as co-authors
+
+**Only attribute real humans** as co-authors when collaborating.

remarkbox/__init__.py

@@ -202,18 +202,7 @@ def main(global_config, **settings):
             session_settings["domain"] = root_domain
 
         factory = SignedCookieSessionFactory(**session_settings)
-        session = factory(request)
-
-        # Log session contents and size on every request
-        import pickle
-        session_dict = dict(session)
-        serialized = pickle.dumps(session_dict)
-        log.info(f"Session total size: {len(serialized)} bytes, keys: {list(session_dict.keys())}")
-        for key, value in session_dict.items():
-            item_size = len(pickle.dumps({key: value}))
-            log.info(f"  Session['{key}'] = {item_size} bytes (type: {type(value).__name__})")
-
-        return session
+        return factory(request)
 
     # setup session factory to use unencrypted but signed cookies.
     # session_factory = SignedCookieSessionFactory(**session_settings)