Close out chains contract and help updates

[TacoRocket]

Summary:

• align chains JSON contracts with the rendered analyst-facing view for credential-path and deployment-path
• gate semantic-high-band loot to supported chains families while keeping the base chains overview ranked-cutoff
• tighten compute-control help and claim boundaries so AzureFox does not imply SSRF, runtime exploitation, or token-minting proof
• refresh the README demo GIF asset

Validation:

• full pre-push guardrail passed: 411 tests passed, 2 deselected
• focused chains/help/output pytest slices also passed during implementation