RFC · linear SPV chain management
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Always linear. Host never exits. SDF_OUT chains SPVs.

WBS  Web BGS · host ground · value|1 · never dies
WBF  Web BGF · measure (step - prev)|1 · drives auto hotswap
SDF  boundary Host↔SPV and SPV↔SPV (normal as must)
SPV  free plug · rides BGF · push_constants from RFC

Files: *.rfc.json
  wb rfc-list
  wb chain-start 0001
  wb chain-tick
  wb chain-auto 6
  wb chain-status

Push constants written to:
  current/push_constants.json
  current/chain.json
  current/step.json