cendor-sdk 1.17.0

Findings-closure wave — a fix for streamed-async checkpointing and multi-agent pipeline-shape
governance parity with the TypeScript SDK. Backwards-compatible (new keyword-only options preserve
today's behaviour); no cendor-core changes.

Fixed

• run.astream(checkpoint=…) now persists (it was accepted but not applied). The async
  streaming entry point took a checkpoint= argument and its docstring promised the same S13
  semantics as run.stream, but the argument was never forwarded to stream_agent_async /
  stream_agents_async — so streamed-async checkpointing was silently a no-op. It now saves per turn
  (single agent) / per turn + segment (team) and done-resumes to a lone terminal RunComplete,
  matching run.stream and the TypeScript twin. Covered by a red-first async test (the twin of the
  sync S13 tests).

Added

• Pipeline-shape governance parity (TS-observed). sequential / parallel / parallel_async
  now accept the honoured per-run surface — retry, on_step, and guardrails (a per-run override
  of each agent's list; decisions collected into Result.guardrail_decisions) — in addition to
  audit / max_turns. supervisor gains session, checkpoint, on_step, guardrails, and
  retry, delegating to run_agents exactly as the TypeScript supervisor rides runAgents
  (run_agents / run_agents_async also forward retry now). This mirrors the TypeScript behaviour
  1:1.

Honest limits

• session / checkpoint are team-only; guardrail_mode is single-agent-only. The pipeline
  shapes (sequential / parallel / parallel_async) pipe or fan out over independent per-agent
  inputs — there is no single conversation to persist or resume — so they don't take session /
  checkpoint; use a handoff team (run([...])) or supervisor for that. guardrail_mode
  ("parallel") applies only to single-agent runs; team and pipeline shapes always gate in blocking
  mode. Both languages behave the same (see multi-agent.md).