v2.5.1 — roster guidance corrected

Corrections found by the multi-agent review of parley-deck-cli 1.41.0. Ships with that release.

Fixed

• The legacy-deck remediation was factually wrong. SKILL.md told agents a legacy deck keeps
  working "until parley roster sync moves it across". roster sync moves nothing across — it
  rebases an existing deck roster onto the machine values, and on a legacy deck it correctly
  reports "nothing to do". The real paths are parley roster migrate (fleet, attended, backed up)
  or roster set per member followed by roster render, and neither was named.
• Membership is the deck file. Documented explicitly: the machine layer seeds values, not
  members, so a deck declaring two participants runs two. A deck declaring no roster shows the
  machine roster marked inherited-roster, and roster render will not commit it without
  --adopt-inherited.
• Bootstrap no longer records roster picks in the §2 table. §2 is a generated view; the
  instruction now names parley roster set and parley roster render. The same contradiction was
  removed from the bundled protocol snapshot.
• New verbs and flags documented: roster render, roster migrate, --all, --explain AGENT,
  --scope deck|machine, and the --confirm-breaking requirement for membership changes.
• Status vocabulary extended: section2-only, inherited-roster, not-in-roster.
• Bundled references/COOPERATION.md resynced to the ratified protocol.

Notable changes per release. Dates are release dates.