Agent Run Contract v1 baseline

[BramVR]

Parent

#70

What to build

Create a versioned Agent Run Contract module and route the current agent prepare and runs flows through it. The contract should own encode/decode, validation, redaction, file writing, State Store metadata shape, and list projections while keeping raw secret values out of all artifacts.

Acceptance criteria

• codemesh-run.json includes an explicit contract version and producer/version metadata.
• Agent Prep writes the contract through the Agent Run Contract module.
• Agent Runs reads list projections through the same contract module rather than a private subset.
• Redaction and no-secret-value tests cover contract file bytes and stored metadata.
• Existing agent prepare/runs/clean e2e coverage stays green.

Blocked by

• Shared Readiness Decision for existing commands #72