Restructure Hydrotech Beam project — KB-integrated layout

New project structure with knowledge base integration:
- kb/ with components, materials, fea, dev generations
- models/ for reference NX files (golden copies)
- studies/ for self-contained optimization campaigns
- deliverables/ for final outputs
- DECISIONS.md decision log (6 decisions tracked)
- BREAKDOWN.md (moved from 1_breakdown/)
- Gen 001 created from intake + technical breakdown

KB extension file: atomizer/shared/skills/knowledge-base-atomizer-ext.md

Refs: DEC-HB-004, DEC-HB-005, DEC-HB-006

projects/hydrotech-beam/kb/components/sandwich-beam.md

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+# Sandwich Beam
+
+**Type:** Primary structural component
+**Material:** Steel (AISI) — see [steel-aisi.md](../materials/steel-aisi.md)
+**Status:** Baseline documented, optimization pending
+
+---
+
+## Description
+
+Sandwich I-beam serving as primary load-bearing member in a test fixture assembly. Cross-section features a core layer flanked by face sheets on top and bottom flanges. Web contains a pattern of lightening holes (circular cutouts) to reduce mass.
+
+## Specifications
+
+| Parameter | Value | Units | Source |
+|-----------|-------|-------|--------|
+| Mass (baseline) | ~974 | kg | NX expression `p173` |
+| Tip displacement (baseline) | ~22 | mm | SOL 101 result |
+| Half-core thickness | 20 (baseline) | mm | DV range: 10–40 |
+| Face thickness | 20 (baseline) | mm | DV range: 10–40 |
+| Hole diameter | 300 (baseline) | mm | DV range: 150–450 |
+| Hole count | 10 (baseline) | — | DV range: 5–15 (integer) |
+| Beam length | ❓ TBD | mm | Gap G1 |
+| Support conditions | ❓ TBD | — | Gap G1 |
+
+## Structural Behavior
+
+*From Technical Breakdown (Gen 001):*
+
+The beam is **bending-dominated**:
+
+| Behavior | Governing Parameters | Notes |
+|----------|---------------------|-------|
+| Bending stiffness (EI) | Face thickness, core thickness | Faces carry bending stress, core carries shear. Stiffness scales ~quadratically with distance from neutral axis |
+| Mass | All four variables | Core and face add material; holes remove material from web |
+| Stress concentrations | Hole diameter, hole spacing | Larger holes → higher SCF at edges. Closely spaced holes can interact |
+| Shear capacity | Core thickness, hole count, diameter | Holes reduce shear-carrying area |
+
+## Design Variable Interactions
+
+1. **Core × Face** — classic sandwich interaction. Optimal stiffness balances core depth (lever arm) vs face material (bending resistance)
+2. **Hole diameter × Hole count** — both remove web material. Large + many could leave insufficient ligament width
+3. **Face × Hole diameter** — thicker faces reduce nominal stress, allowing larger holes
+4. **Core × Hole diameter** — core thickness determines web height, constrains max feasible hole diameter
+
+## Key Risk
+
+> ⚠️ Baseline FAILS displacement constraint (22 mm vs 10 mm target). Optimizer must increase stiffness by >50% while reducing mass. Feasible region may be tight.
+
+## History
+
+- **Gen 001** (2026-02-09): Initial documentation from intake + technical breakdown