[contracts] Define RootfieldRegistry URI boundary policy

[FlowmemoryAI]

Objective

Decide and document the v0 policy for metadataURI and evidenceURI so future agents know whether URI fields stay advisory strings, get length caps, or move toward hash/CID-only patterns.

Allowed folders

• docs/DECISIONS/
• docs/SECURITY_MODEL.md
• contracts/FLOWPULSE_SCHEMA.md
• contracts/RootfieldRegistry.sol only if the accepted policy requires a minimal skeleton change
• tests/ only if contract behavior changes

Forbidden folders

• apps/
• services/
• hardware/
• research/
• crypto/
• Tokenomics, L1/appchain design, production deployment config

Acceptance criteria

• A decision record states the v0 URI policy and rejected alternatives.
• The policy explicitly addresses on-chain log bytes, sensitive data, heavy data, and verifier responsibility.
• If contract behavior changes, matching tests are added.
• If no contract behavior changes, the issue is closed with docs only.

Risk level

Medium

Recommended worktree/agent

E:\FlowMemory\flowmemory-contracts / Protocol Contracts Agent

Scope guard

Do not expand into storage economics, token design, or deployment planning.