feat(processes): expose process as a knowledge type

Task 4 of #582. Add 'process' to the knowledge route _VALID_TYPES and to the
get_knowledge_counts facet + total. query_knowledge/_apply_type_filter already
handle arbitrary note_type, so listing by type=process works unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/fabledassistant/routes/knowledge.py

@@ -10,7 +10,7 @@ logger = logging.getLogger(__name__)
 
 knowledge_bp = Blueprint("knowledge", __name__, url_prefix="/api/knowledge")
 
-_VALID_TYPES = {"note", "person", "place", "list", "task", "plan"}
+_VALID_TYPES = {"note", "person", "place", "list", "task", "plan", "process"}
 _VALID_SORTS = {"modified", "created", "alpha", "type"}