Global chat session endpoints removed from the Everruns API
The two endpoints that looked up a per-user Platform Chat session by tag are removed. A chat thread is now an ordinary session created with POST /v1/sessions and bound to an agent.
After upgrading, POST /v1/sessions/chat returns 405 and POST /v1/sessions/chat/voice returns 404. Sessions already tagged global-chat stay listed and readable through the normal session routes, and the Platform Chat harness is unchanged.
See Platform Chat and #3278.