Get a Tally conversation turn with acceptance metadata

Returns the authoritative turn record (status, error, linked assistant message id, stream state) plus the refreshed conversation, recent messages, and a nullable server-derived Bookkeeping Startup progress projection. The projection updates through this existing poll without exposing workspace paths, organization ids, raw errors, or model-authored progress. Completed turns include a sanitized acceptance block — provider, model, provider attempts, iteration/token/cost/tool-byte runtime totals, tool call names with read-only flags, failover and mutation-boundary indicators, and continuation state — with no raw tool inputs, tool outputs, or prompt text. The live acceptance harness polls this route to prove model identity, runtime budgets, and safety boundaries.