Add GigaBIT M1 frame stiffness characterization project

- 3 studies: sensitivity (Method D), stiffness sweep (Method B), robustness
- Atomizer specs with run matrices, Zernike annular OPD extractor
- War-room validated hybrid B+D method

projects/gigabit-m1-frame-stiffness/studies/02_stiffness_sweep_method_b/README.md

@@ -0,0 +1,30 @@
+# Study 02 — Stiffness Sweep (Method B)
+
+**Type:** Parametric — CBUSH Spring-to-Ground Sweep
+**Runs:** 22 (2 validation + 10 K_vert sweep + 10 K_lat sweep)
+**Model:** CBUSH elements at 5 interface points, offset ground nodes (−10mm Z)
+
+## What This Does
+
+Replaces fixed BCs with CBUSH springs. Sweeps translational stiffness from 1e4 → 1e10 N/m on log scale. Two independent campaigns:
+- Campaign 1: Sweep K_vert (laterals rigid)
+- Campaign 2: Sweep K_lat (verticals rigid)
+
+Finds the **knee point** where ΔWFE crosses the 1.0 nm budget.
+
+## .sim Setup Required
+
+1. Create 5 ground nodes (offset −10mm in −Z from each support node)
+2. SPC 123456 on all ground nodes
+3. Remove existing SPCs on 5 support nodes
+4. Create 5 CBUSH elements (support → ground, global coords)
+5. Create 2 PBUSH properties: 8001 (vertical, K=$K_vert) and 8002 (lateral, K=$K_lat)
+6. Create 2 NX expressions: `K_vert`, `K_lat` (default = 1e12)
+
+## Extractor
+
+Same as Study 01: Zernike annular OPD, 50 modes, J5+ filtered, annular aperture.
+
+## Output
+
+ΔWFE vs K curves → knee points → recommended minimum stiffness for StarSpec.