cendor-sdk 1.16.0

SDK telemetry wave — structural signals for RAG, memory, orchestration, checkpoints, tools, and MCP
become first-class cendor.sdk spans, so an OTel backend (or Cendor Monitor) renders each as its own
domain. Zero core changes — the new signals ride cendor-core's bus and the existing
live_spans() scope; content rules are unchanged (labels/ids/counts only, never message bodies).

Added

• RAG spans (rag.assemble / rag.compress): an always-on retriever's context_budget assembly
  (contextkit AssemblyReport) and squeeze compression (CompressionEvent) now surface as cendor.sdk
  child spans inside a live_spans() run — budget/used, blocks kept vs dropped, token deltas, technique.
• Memory spans (memory.load / memory.save): a run that reads/writes a Session emits a span
  carrying the session id, turn count, and byte size.
• Orchestration handoff spans (orchestration.handoff): each transfer_to_<peer> handoff emits an
  edge (from-agent → to-agent, segment, transfer tool) so a monitor reconstructs the multi-agent graph
  from rows rather than parsing trace-id families.
• Checkpoint spans (checkpoint.save / checkpoint.resume): a Checkpointer write and a resume
  decision (finished or unfinished) emit spans carrying the run id, done flag, and turn count.
• Tool source + outcome: every execute_tool span now carries cendor.tool.source
  (local | mcp, + cendor.tool.mcp.server/transport) and cendor.tool.outcome
  (ok | error | blocked). A tool_call guardrail block — which runs no tool and so emits no
  ToolCall — now emits a dedicated execute_tool {name} span with outcome="blocked" +
  cendor.tool.blocked_by (the guardrail name; never the reason text).
• MCP server attribution: load_mcp_tools(session, server=…, transport=…) tags each tool's spans
  with the MCP server + transport and emits mcp.connect / mcp.list_tools lifecycle spans, so a
  monitor attributes tool calls per server. The labels are optional and non-secret.

Honest limits

• The new domain telemetry rides the live path (live_spans); the post-hoc span_tree continues
  to render the LLM/tool tree from Result (and now also stamps tool source/outcome).
• The tool-source registry is process-global; a tool-name collision across two MCP servers is
  last-writer-wins.