Rename the persistent agent integration to Sybil Agent

Use SYBIL_AGENT_BASE_URL and SYBIL_AGENT_API_KEY with the renamed sybil-agent
service. Update errors, API documentation, and test fixtures while retaining the
existing room protocol and browser storage keys for compatibility.

Validation: 44 server tests, 51 web tests, and both production builds.

web/src/lib/agent-room-presentation.ts

@@ -26,7 +26,7 @@ const entryId = (message: Message): bigint | undefined => {
 const toolId = (message: Message) => typeof data(message).toolCallId === 'string' ? String(data(message).toolCallId) : message.id;
 
 /**
- * Pi sends messages and activity as separate frames. This adapter publishes them
+ * Sybil Agent sends messages and activity as separate frames. This adapter publishes them
  * as one room snapshot and latches transcript typing off when a new public reply
  * arrives. An unchanged busy frame cannot restore the old turn's indicator.
  * Actual activity remains untouched for the sidebar, workers, and queue display.