cendor-sdk 1.9.0

gen_ai.conversation.id grouping for multi-turn runs. Backward-compatible (additive, opt-in).

Added

• live_spans(..., conversation_id=…) and span_tree(result, ..., conversation_id=…) now
  accept an optional conversation/session id (e.g. your SQLiteSessionStore key). When given, the
  root agent.run span carries it as the OpenTelemetry gen_ai.conversation.id semantic-convention
  attribute, so a backend can group the runs of one multi-turn conversation. Omitted by default (no
  key leaks when you aren't grouping). Libs-only users can pass any gen_ai.* attribute — including
  gen_ai.conversation.id — through cendor.core.otel.span(...)'s existing attributes argument.
  See https://cendor.ai/docs/observability