Adds automated feedback architecture research to gsd-phase-researcher,
enforces it as Dimension 8 in gsd-plan-checker, and introduces
{phase}-VALIDATION.md as the per-phase validation contract.
Ensures every phase plan includes automated verify commands before
execution begins. Opt-out via workflow.nyquist_validation: false.
Closes#122 (partial), related #117
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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