Add text knowledge

Create or replace a text knowledge source. To edit, read get_knowledge_source(includeInactive=true), then pass its text sourceId with the complete replacement text; omitted sourceId uses existing deterministic text ingestion identity. Never use a file/URL/website ID to edit text. Creation/replacement embeds content and can store it inactive on quota; read result active/quotaExceeded and follow get_knowledge_source/get_knowledge_usage. Reconcile sources after ambiguous failures; do not invent a replacement ID. Required permission: knowledge:write.