v0.91.0

Added

• synapse causality otel projects the coordination-causality graph onto
  OpenTelemetry spans: one trace per task (a root span covering the task's
  recorded lifetime, one child span per coordination event) with cross-task
  dependency/contention edges carried as span links — "this claim
  proceeded because that release freed its paths" renders as a first-class
  link in any trace viewer. Ids are deterministic derivations of the task id
  and event sequence, so re-exporting the same log yields identical spans.
  --out FILE writes the span records as JSON with no new dependency;
  --endpoint URL pushes OTLP over HTTP through the official exporter
  behind the new optional otel extra. A failed push exits non-zero with
  the exporter's verdict, and taskless events are counted in the summary
  rather than silently dropped.
• synapse causality traces coordination causality across federated hubs:
  --peer HUB=PATH (repeatable) merges the named hubs' event logs in the
  deterministic multi-hub order, events are addressed as HUB:SEQ
  (--hub-id names the primary log), and an edge whose endpoints two
  different hubs authored is tagged federation with the recorded
  relation it derives from as its basis. Cross-hub precedence is
  clock-ordered evidence — hubs share no sequence — and the queries stay
  read-only and observe-only, like the multi-hub fold. contention
  remains single-hub and refuses --peer.