[CTX-0080] feat: reconcile DevTools identity, platform, version, quality contracts

[Xuepoo]

Priority: P1 | Area: contracts | Labels: feat, P1 | Milestone: v0.1.0 | Task: CTX-0080

Reconciles DevTools identity, platform, version, and quality contracts to ensure fail-closed validation and comprehensive testing.

Changes

• Add platform contract validation (Node.js, Bun, Deno runtime detection)
• Add protocol boundary enforcement (strict DevTools Protocol version, method allowlists)
• Add comprehensive validation layer (socket path, process existence, auth token format)
• Extend workflow import with offline/pinned modes, budget tracking
• Add required CI status checks tracking
• Update quality gates to enforce contract validation
• Add comprehensive test coverage for all new contracts

Testing

• All existing tests pass (634 tests)
• Added new test suites: platform-contract, protocol-boundary, validation, workflow-import-budget
• Quality gates pass: format, lint, type-check, test, cargo-check

Closes #141

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