docs: add QUICK_REF + workflow OS + 2026Q1 roadmap

docs/WORKFLOWS/VALIDATE.md

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+# Workflow: VALIDATE
+
+_Last updated: 2026-01-29 (Mario)_
+
+## Goal
+Give the user confidence that the study will run correctly:
+- correct model chain
+- DV bounds sane
+- objectives/constraints correctly sourced
+- spec is runnable
+
+## Primary UI
+- Checklist + Parameters table
+
+## Secondary UI
+- Canvas visualization
+
+## Outputs
+- Validation report (errors/warnings)
+- "Ready to Run" state