Fix project isolation: Make loadChatHistory respect active project sessions

- Modified loadChatHistory() to check for active project before fetching all sessions
- When active project exists, use project.sessions instead of fetching from API
- Added detailed console logging to debug session filtering
- This prevents ALL sessions from appearing in every project's sidebar

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.venv/lib/python3.11/site-packages/pydantic/experimental/missing_sentinel.py

@@ -0,0 +1,5 @@
+"""Experimental module exposing a function a `MISSING` sentinel."""
+
+from pydantic_core import MISSING
+
+__all__ = ('MISSING',)