Why: freeze the direction for 10-100 user multi-project collaboration storage (PostgreSQL team tier, migration, staged multi-instance) before U1+U2 implementation starts.
Evidence: static review record and SELF audit receipt included; user approval recorded in Dev task card 2026-10-11 (instruction to start the transformation per the plan).
Impact: docs only - new proposal, index entry, review record, audit receipt; no code or runtime change.
Refs: Dev .task/feature-collaboration-storage-plan.md; plan section 5 names U1+U2 as the first increment.
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