Validate OpenSpec CLI JSON contracts

[VeryComplexAndLongName]

Validates OpenSpec CLI JSON at the core boundary before data reaches delivery adapters.

• adds per-command structural validators that allow additive unknown fields
• returns typed, bounded compatibility diagnostics for malformed or incompatible output
• normalizes OpenSpec 1.7.0 status output without progress from artifact completion
• confirms standalone overview exposes actionable compatibility guidance
• bumps core minor and server/extension patch versions

Verification:

• npm run verify (274 tests)
• npm run build
• openspec change validate --strict openspec-cli-contract-validation
• live execution of all seven JSON wrappers against OpenSpec CLI 1.7.0, with create/archive isolated to a temporary workspace